Communication system, information processing apparatus, server, and communication method

ABSTRACT

A first information processor transmits a bubble packet to a second communication control unit for leaving transmission record in a first communication control unit by way of the first communication control unit, a second information processor transmits a reply packet to one or more ports including at least the bubble packet transmitting port as the port of the first communication control unit used in transmission of bubble packet, and the first information processor receives the reply packet transmitted from the second information processor by way of the second communication control unit. In this configuration, the invention presents a communication system capable of establishing communication between plural information processors for communicating by way of communication control unit (NAT).

This application is a U.S. National Phase Application of PCTInternational Application PCT/JP2004/015721 dated Oct. 22. 2004.

TECHNICAL FIELD

The present invention relates to communication system or the like forestablishing communications between plural information processors.

BACKGROUND ART

First, classification of NAT (network address translation) is explained.The NAT includes the transmission port assigning rule and receptionfilter rule, and the NAT is classified according to their combination.The transmission port assigning rule is divided into a cone type inwhich, not depending on the packet destination (IP address, port), whenthe port of NAT local side (for example, LAN side) information processorand the IP address are the same, the port of the global side (forexample, the Internet or WAN side) assigned to the NAT is the same, anaddress sensitive type in which a new port is assigned for each packetdestination address, and a port sensitive in which a new port isassigned for each destination port of packet. The reception filter rulefor judging possibility of reception of packet from the local side tothe port transmitting the packet from the NAT local side is divided intoan address sensitive filter for receiving the packet only from theaddress transmitting the packet from the port, a port sensitive filterfor receiving the packet only from the port transmitting the packet fromthe port, and no filter having no filter. By combining the transmissionport assigning rule and reception filter rule, the NAT can be classifiedinto the following type types.

Full cone NAT: Transmission port assigning rule of cone type, andreception port filter rule of no filter.

Restricted cone NAT: Transmission port assigning rule of cone type, andreception port filter rule of address sensitive filter.

Port restricted cone NAT: Transmission port assigning rule of cone type,and reception port filter rule of port sensitive filter.

Address sensitive symmetric NAT: Transmission port assigning rule ofaddress sensitive type, and reception port filter rule of addresssensitive filter.

Port sensitive symmetric NAT: Transmission port assigning rule of portsensitive type, and reception port filter rule of port sensitive filter.

In the NAT communication, it has been proposed to establishcommunications between PC1 and PC2 without using server as shown in FIG.40.

In this case, probably, there is a combination of NATs unable toestablish communications. In FIG. 40, when communicating from PC1 ofinformation processor connected to NAT1 local side to PC2, let us callNAT1 as sending side NAT, and NAT2 as receiving side NAT. Hence,combination of NATs capable of establishing communications between PC1and PC2 is as shown in FIG. 41. Abbreviations of NATs in FIG. 41 arespecifically described in the following preferred embodiments. In FIG.41, connection of *1 has been known hitherto. Even in the combination ofNATs capable of establishing communications, connection of *3 involvesan uncertainty because communications cannot be established unless theport number differential of NAT is known and the position of the latestport of receiving side NAT is known.

As prior conditions for establishing communications between informationprocessors, it is desired to detect the range of ports of NAT passingthrough the bubble packet (the packet sent in order to leavecommunication record in the NAT) transmitted from one informationprocessor.

DISCLOSURE OF THE INVENTION

It is hence an object of the invention to present communication systemor the like capable of securely establishing communications betweenplural information processors for communicating by way of acommunication control unit for controlling the communications.

It is other object of the invention to present communication system orthe like capable of detecting the range of ports in the communicationcontrol unit allowing to pass the bubble packet transmitted from theinformation processor.

To achieve the object, the communication system of the inventioncomprises a first information processor, a second information processor,a first communication control unit for controlling the communication ofthe first information processor, a second communication control unit forcontrolling the communication of the second information processor, and aserver for establishing the communication between the first informationprocessor and second information processor, in which the firstinformation processor includes a bubble packet transmitter for sending abubble packet for leaving transmission record in the first communicationcontrol unit in the second communication control unit by way of thefirst communication control unit, and a reply packet receiver forreceiving the reply packet sent from the second information processor byway of the second communication control unit, to the bubble packettransmitting port which is a port of the first communication controlunit used in transmission of the bubble packet, and the secondinformation processor includes a reply packet transmitter for sendingthe reply packet to one or more ports including at least the bubblepacket transmitting port.

In this configuration, by sending the reply packet to the port of thefirst communication control unit assigned by transmission of bubblepacket, communication between the first information processor and secondinformation processor can be established.

The first information processor of the invention is a first informationprocessor communicating with the second information processor by way ofthe first communication control unit for controlling the communicationof the first information processor and the second communication controlunit for controlling the communication of the second informationprocessor, and it includes a bubble packet transmitter for sending abubble packet for leaving transmission record in the first communicationcontrol unit to the second communication control unit by way of thefirst communication control unit, and a reply packet receiver forreceiving the reply packet sent from the second information processor byway of the second communication control unit, to the bubble packettransmitting port which is a port of the first communication controlunit used in transmission of the bubble packet.

In this configuration, the bubble packet transmitting port used inestablishing communication with the second information processor can beassigned in the first communication control unit by sending the bubblepacket, and by receiving the reply packet sent to the bubble packettransmitting port, communication between the first information processorand second information processor can be established.

The server of the invention is a server for establishing communicationbetween the first information processor and second information processorby way of the first communication control unit for controllingcommunication of the first information processor and the secondcommunication control unit for controlling communication of the secondinformation processor, and it includes an information transmitter andreceiver for transmitting and receiving information between the firstinformation processor and second information processor, a characteristicdetermination unit for determining the characteristic of the firstcommunication control unit and second communication control unit, and adetermination unit for transmitting and receiving for determining eitherone of the first information processor and second information processoras transmission side (sending side information processor) and other oneas reception side (receiving information processor) according to thedetermination by the characteristic determination unit.

In this configuration, depending on the characteristic of the firstcommunication control unit and second communication control unit, one ofthe first information processor and second information processor isdetermined as the transmission side and other as reception side so as toestablish communication between the first information processor andsecond information processor.

The server of the invention is also a server for establishingcommunication between the first information processor and secondinformation processor by way of the first communication control unit forcontrolling communication of the first information processor and thesecond communication control unit for controlling communication of thesecond information processor, and it includes a detector for detectingport number for receiving a range detecting packet for detecting therange of ports including the bubble packet transmitting port which is aport of the first communication control unit used in transmission ofbubble packet for leaving transmission record in the first communicationcontrol unit to the second communication control unit from the firstinformation processor, and detecting the position of the port of thefirst communication control unit allowing to pass this range detectingpacket, and a port number information transmitter for detecting portnumber for sending the port information for detecting showing theposition of the port detected by the detector for detecting port numberto the first information processor.

In this configuration, the port information for detecting used fordetecting the range of ports including the bubble packet transmittingport in the first information processor can be sent to the firstinformation processor.

The server of the invention is further a server for establishingcommunication between the first information processor and secondinformation processor by way of the first communication control unit forcontrolling communication of the first information processor and thesecond communication control unit for controlling communication of thesecond information processor, and it includes a target port transmitterfor transmitting bubble packet for sending the target port informationfor transmitting bubble packet showing the position of the target portfor transmitting bubble packet which is a port in the secondcommunication control unit as the target of transmission of bubblepacket for leaving transmission record in the first communicationcontrol unit by the first information processor to the first informationprocessor.

In this configuration, the position of the port as the target oftransmission of bubble packet can be noticed to the first informationprocessor by the target port information for transmitting bubble packet.

The communication system of the invention is a communication systemcomprising an information processor, a communication control unit forcontrolling the communication of the information processor, and aserver, in which the information processor includes a bubble packettransmitter for transmitting one or more bubble packets for leavingtransmission record in the communication control unit by way of thecommunication control unit, and a range detection packet transmitter forsending the range detecting packet used in detection of range of portsincluding one or more bubble packet transmitting ports as ports of thecommunication control unit used in transmission of one or more bubblepackets to the server, and the server includes a range detector forreceiving the range detecting packet, and detecting the range of portsincluding the one or more bubble packet transmitting ports on the basisof the range detecting packet.

In this configuration, by the range detecting packet transmitted fromthe information processor, the range of ports including the bubblepacket transmitting port can be detected in the server. By sending apacket from other device to the range of ports including the detectedbubble packet transmitting port, this packet can be received in theinformation processor.

The communication system of the invention is a communication systemcomprising an information processor, a communication control unit forcontrolling the communication of the information processor, and aserver, in which the information processor includes a bubble packettransmitter for transmitting one or more bubble packets for leavingtransmission record in the communication control unit by way of thecommunication control unit, a range detection packet transmitter forsending the range detecting packet used in detection of range portsincluding one or more bubble packet transmitting ports as ports of thecommunication control unit used in transmission of one or more bubblepackets for leaving transmission record in the communication controlunit to the server by way of the communication control unit, a portinformation receiver for detecting for receiving the port informationfor detecting showing the position of the port of the communicationcontrol unit allowing the range detecting packet to pass, and a rangedetector for detecting the range of ports including the one or morebubble packet transmitting ports on the basis of the port informationfor detecting received in the port information receiver for detecting,and the server includes a detector for detecting port number forreceiving the range detecting packet and detecting the position of theport of the communication control unity allowing to pass the rangedetecting packet, and a port number information transmitter fordetecting port number for sending the port information for detectingshowing the position of the part detecting the detector for detectingport number to the information processor.

In this configuration, by the range detecting packet transmitted fromthe information processor, the range of ports including the bubblepacket transmitting port can be detected. By sending a packet from otherdevice to the range of ports including the detected bubble packettransmitting port, this packet can be received in the informationprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of configuration of communication system inpreferred embodiment 1 of the invention.

FIG. 2 is a block diagram of configuration of first informationprocessor in the preferred embodiment.

FIG. 3 is a block diagram of configuration of second informationprocessor in the preferred embodiment.

FIG. 4 is a block diagram of configuration of first and second serversin the preferred embodiment.

FIG. 5 is a flowchart of operation of communication system in thepreferred embodiment.

FIG. 6 is a flowchart of determination process of transmission andreception in the preferred embodiment.

FIG. 7 is an explanatory diagram of determination of characteristic ofcommunication control unit in the preferred embodiment.

FIG. 8 is an explanatory diagram of determination of characteristic ofcommunication control unit in the preferred embodiment.

FIG. 9 is an explanatory diagram of determination of characteristic ofcommunication control unit in the preferred embodiment.

FIG. 10 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 11 is an explanatory diagram of detection of port numberdifferential in the preferred embodiment.

FIG. 12 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 13 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 14 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 15 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 16 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 17 is a diagram of combination of characteristics of communicationcontrol units that can be connected in the preferred embodiment.

FIG. 18 is a block diagram of configuration of first informationprocessor in preferred embodiment 2 of the invention.

FIG. 19 is a block diagram of configuration of second informationprocessor in the preferred embodiment.

FIG. 20 is a block diagram of configuration of first and second serversin the preferred embodiment.

FIG. 21 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 22 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 23 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 24 is a block diagram of configuration of communication system inpreferred embodiment 3 of the invention.

FIG. 25 is a block diagram of configuration of communication system inpreferred embodiment 4 of the invention.

FIG. 26 is a block diagram of configuration of first informationprocessor in the preferred embodiment.

FIG. 27 is a block diagram of configuration of second informationprocessor in the preferred embodiment.

FIG. 28 is a block diagram of configuration of server in the preferredembodiment.

FIG. 29 is a flowchart of determination process of transmission andreception in the preferred embodiment.

FIG. 30 is an explanatory diagram of determination of characteristic ofcommunication control unit in the preferred embodiment.

FIG. 31 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 32 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 33 is a flowchart of process of establishment of communication inthe preferred embodiment.

FIG. 34 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 35 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 36 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 37 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 38 is an explanatory diagram of specific example in the preferredembodiment.

FIG. 39 is a diagram of combination of characteristics of communicationcontrol units that can be connected in the preferred embodiment.

FIG. 40 is a diagram showing an example of communication system.

FIG. 41 is a diagram showing combination of conventional NATs that canbe connected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred Embodiment 1

A communication system in preferred embodiment 1 of the invention isdescribed while referring to the accompanying drawings.

FIG. 1 is a block diagram of configuration of communication system inthe preferred embodiment. In FIG. 1, the communication system in thepreferred embodiment comprises first information processor 1, secondinformation processor 2, first communication control unit 3, secondcommunication control unit 4, first server 6, and second server 7. Firstcommunication control unit 3, second communication control unit 4, firstserver 6, and second server 7 are connected by way of wired or wirelesscommunication network 5. Communication network 5 is, for example, theInternet.

In FIG. 1, first information processor 1 and second informationprocessor 2 are connected respectively to first communication controlunit 3 and second communication control unit 4, but other devices may bealso connected to first communication control unit 3 and secondcommunication control unit 4.

FIG. 2 is a block diagram of configuration of first informationprocessor 1. In FIG. 2, first information processor 1 comprisescommunication unit 11, bubble packet transmitter 12, range detectionpacket transmitter 13, reply packet receiver 14, port numberdifferential detection packet transmitter 15, target port receiver fortransmitting bubble packet 16, range receiver 17, port numberdifferential receiver 18, and reply packet transmitter 19.

Communication unit 11 communicates between bubble packet transmitter 12or other internal constituent elements in first information processor 1and first communication control unit 3.

Bubble packet transmitter 12 transmits a bubble packet to secondcommunication control unit 4 by way of communication unit 11 and firstcommunication control unit 3. The bubble packet is a packet for leavingtransmission record in first transmission control unit 3 in order toestablish communication between first information processor 1 and secondinformation processor 2. Establishment of communication means to startpeer-to-peer communication without resort to server between firstinformation processor 1 and second information processor 2. Leaving ofcommunication record is to assign port (open port) for receiving atransmission packet described below, in first communication control unit3. Generally, a bubble packet is transmitted in order to leavetransmission record, but as a result of transmission of a specifiedpacket, the transmission record for receiving the transmission packetmay be left in first communication control unit 3 (in this case, thespecified packet leaving the transmission record is the bubble packet).This bubble packet may contain certain information or no information.The bubble packet is transmitted by connectionless protocol such as UDP(user datagram protocol).

Range detection packet transmitter 13 sends a range detecting packet tofirst server 6 or second server 7. This range detecting packet is usedfor detecting the range of ports including the bubble packettransmitting port. The bubble packet transmitting port is a port offirst communication control unit 3 used in transmission of bubblepacket. The range detecting packet is transmitted before the bubblepacket is transmitted and/or after bubble packet is transmitted. Whensending the range detecting packet before and after transmission ofbubble packet, the range detecting packet may be sent to differentaddresses (IP addresses) before and after. The range detecting packet istransmitted by UDP or TCP (transmission control protocol). This rangedetecting packet may contain certain information or no information.

Reply packet receiver 14 receives the transmission packet sent fromsecond information processor 2 by way of second communication controlunit 4. This reply packet is transmitted to the port assigned bytransmission of bubble packet in first communication control unit 3,that is, to the bubble packet transmitting port. By receiving the replypacket, communication is established between first information processor1 and second information processor 2. The reply packet is transmitted,for example, by UDP. The reply packet may contain certain information orno information.

Port number differential detection packet transmitter 15 sends the portnumber differential detecting packet for detecting the port numberdifferential in first communication control unit 3 to first server 6 byway of first communication control unit 3. The port number differentialis the differential (interval) of ports used (assigned) continuously.For example, when the port number differential is 1, the port used nextto port number 2000 is port number 2001. When the port numberdifferential is 2, the port used next to port number 2000 is port number2002. The port number differential detecting packet is transmitted, forexample, by UDP or TCP. The port number differential detecting packetmay contain certain information or no information.

Target port receiver for transmitting bubble packet 16 receives targetport information for transmitting bubble packet. Target port informationfor transmitting bubble packet is the information indicating theposition of target port for transmitting bubble packet which is thetarget port for transmitting bubble packet in second communicationcontrol unit 4. For example, when port number of target port fortransmitting bubble packet is included in the target port informationfor transmitting bubble packet, the position of target port fortransmitting bubble packet can be known from first information processor1. The target port for transmitting bubble packet is, for example, aport of transmitting and receiving information by second informationprocessor 2 to and from first server 6.

The components from bubble packet transmitter 12 to target port receiverfor transmitting bubble packet 16 are used when first informationprocessor 1 operates as information processor at transmission side. Theinformation processor at transmission side is the side of sending thebubble packet when establishing communication between the firstinformation processor 1 and second information processor 2. In thispreferred embodiment, unless the transmission and reception areexchanged as described later, the bubble packet sending side and thecommunication (connection) requesting side (sending/calling side) arethe same, and the transmission side is also the communication requestingside.

On the other hand, the information processor at the opposite side is theinformation processor at the reception side, that is the informationprocessor at the side of sending reply packet to the bubble packet. Inthe preferred embodiment, unless the transmission and reception areexchanged, the reply packet sending side and the side receiving thecommunication request (receiving side) are the same, and hence thereception side is also the communication request receiving side. Thecomponents from range receiver 17 to reply packet transmitter 19described below are used when the first information processor 1 operatesas the information processor at reception side.

Range receiver 17 receives range information. The range information isthe information showing the range of ports for sending the reply packetto second communication control unit 4 from reply packet transmitter 19.The range information shows the range of ports including the bubblepacket transmitting port in second communication control unit 4 (portused in transmission of bubble packet from second information processor2 to first communication control unit 3), for example, by the portnumber. The range information may show the range of ports by indicatingthe upper limit of ports only, or by the lower limit of ports only, orthe range of ports may be indicated by both upper limit and lower limitof ports. The upper limit of ports refers to the port of the greaterport number, and the lower limit of ports refers to the port of thesmaller port number.

Port number differential receiver 18 receives port number differentialinformation which is the information showing the port numberdifferential in second communication control unit 4.

Reply packet transmitter 19 sends a reply packet to one or more portsincluding at least the bubble packet transmitting port in secondcommunication control unit 4. At this time, by sending the reply packetto the port in the range showing the range information received in rangereceiver 17, the reply packet can be sent to the ports including thebubble packet transmitting port in second communication control unit 4.When sending reply packets to two or more ports, the reply packet issent in every port number differential indicated by port numberdifferential information. As a result, when the port number differentialindicated by port number differential information is 2 or more, thereply packet can be sent efficiently. The reply packet may be also sentfrom the port making communication with first server 6 by firstinformation processor 1.

FIG. 3 is a block diagram of configuration of second informationprocessor 2. Second information processor 2 comprises communication unit21, bubble packet transmitter 22, range detection packet transmitter 23,reply packet receiver 24, packet transmitter for detecting port numberdifferential 25, target port receiver for transmitting bubble packet 26,range receiver 27, port number differential receiver 28, and replypacket transmitter 29. Herein, the components from communication unit 21to reply packet transmitter 29 in second information processor 2 aresame as communication unit 11 to reply packet transmitter 19 in firstinformation processor 1, except that first information processor 1,first communication control unit 3, second information processor 2, andsecond communication unit 4 are exchanged, and detailed description isomitted.

The components from bubble packet transmitter 22 to target port receiverfor transmitting bubble packet 26 in second information processor 2 areused when second information processor 2 operates at transmission side.On the other hand, range receiver 27 to reply packet transmitter 29 isused when second information processor 2 operates at reception side.

First communication control unit 3 is to control communication of firstinformation processor 1, and controls communication of local side (firstinformation processor 1 side) and global side (communication network 5side), by using the so-called NAT. Types of NAT include full cone NAT,restricted cone NAT (R NAT), port restricted cone NAT (PR NAT), addresssensitive symmetric NAT (AS NAT), and port sensitive symmetric NAT (PSNAT).

Second communication control unit 4 is to control communication ofsecond information processor 2, by using the NAT, same as firstcommunication control unit 3. As combination of first communicationcontrol unit 3 and second communication control unit 4, except forcombination of PS NAT at both, communication between first informationprocessor 1 and second information processor 2 can be established. Infirst communication control unit 3 and second communication control unit4, ports are assigned so that the port numbers may increase or decreasein every specified port number differential. In the followingexplanation, the ports are assigned so that the port numbers mayincrease.

FIG. 4 is a block diagram of configuration of first server 6 and secondserver 7. In FIG. 4, first server 6 comprises communication unit 61,information transmitter and receiver 62, characteristic determinationunit 63, determination unit for transmitting and receiving 64, targetport transmitter for transmitting bubble packet 65, range detector 66,range transmitter 67, port number differential detector 68, and portnumber differential information transmitter 69. Second server 7comprises communication unit 71.

Communication units 61, 71 communicate between information transmitterand receiver 62 and other parts of first server 6, and first informationprocessor 1 and second information processor 2. Communication unit 61and communication unit 71 exchange information between servers. Insecond server 7, only communication unit 71 is shown, but other elementsmay be also added aside from communication unit 71.

Information transmitter and receiver 62 transmits and receivesinformation to and from first information processor 1 and secondinformation processor 2. Transmission or reception of information byinformation transmitter and receiver 62 is carried out by way ofcommunication unit 61 and communication unit 71.

Characteristic determination unit 63 determines the characteristic offirst communication control unit 3 and second communication control unit4. Herein, the characteristic of first communication control unit 3 andsecond communication control unit 4 refers to the type of NAT used infirst communication control unit 3 and others. Hence, the characteristicof first communication control unit 3 is determined to be, for example,full cone NAT or AS NAT.

Determination unit for transmitting and receiving 64 determines eitherone of first information processor 1 and second information processor 2as transmission side (sending side information processor) and other asreception side (receiving side information processor) depending on theresult of determination by characteristic determination unit 63. As aresult of this determination, the communication control unit forcontrolling communication of sending side information processor, out offirst communication control unit 3 and second communication control unit4, is the sending side communication control unit, and the communicationcontrol unit for controlling communication of receiving side informationprocessor side is the receiving side communication control unit.

Target port transmitter for transmitting bubble packet 65 sends thetarget port information for transmitting bubble packet indicating theposition of target port for transmitting bubble packet in receiving sidecommunication control unit to sending side information processor.

Range detector 66 receives the range detecting packet sent from thesending side information processor, and detects the range of portsincluding the bubble packet transmitting port on the basis of thereceived range detecting packet. For detection of port range, the portnumber included in the header of the range detecting packet may beacquired, and recorded in a specified memory or the like. That is, therange detecting packet may be sent from the sending side informationprocessor to communication unit 61, or may be once sent to communicationunit 71 of second server 7, and received by way of communication unit61. In the later case, IP addresses are differential in first server 6and second server 7.

Range transmitter 67 sends range information which is the informationshowing the range of ports including the bubble packet transmitting portdetected by range detector 66 to the receiving side informationprocessor.

Port number differential detector 68 receives the port numberdifferential detecting packet sent from the sending side informationprocessor by way of the sending side communication control unit. Theport number differential detecting packet is a packet used for detectionof port number differential in the sending side communication controlunit. Port number differential detector 68 detects the port numberdifferential in the sending side communication control unit on the basisof the received port number differential detecting packet.

Port number differential information transmitter 69 sends the portnumber differential information which is the information showing theport number differential detected by port number differential detector68 to the receiving side information processor.

The operation of communication system of the preferred embodiment isexplained. Referring now to the flowchart in FIG. 5, the communicationmethod until start of communication between first information processor1 and second information processor 2 is explained.

(Step S101) Characteristic determination unit 63 of first server 6determines the characteristic of first communication control unit 3 andsecond communication control unit 4, and it is determined which one offirst information processor 1 and second information processor 2 is attransmission side or reception side.

Herein, communication between information processors cannot beestablished if PS NAT is used at transmission side and AS NAT is used atreception side, or if PR NAT is used at transmission side and AS NAT orPS NAT is used at reception side, and hence the transmission side andreception side must be determined properly. If PS NAT is used at bothtransmission side and reception side, communication between informationprocessors cannot be established in the method of this preferredembodiment. In this case, the reason of failure in establishment ofcommunication is explained later.

(Step S102) Sending bubble packet from sending side informationprocessor to receiving side communication control unit, a reply packetis sent from the receiving side information processor to one or moreports including at least the bubble packet transmitting port, andcommunication is established. The detail of process at steps S101 andS102 is described below.

FIG. 6 is a flowchart of process of determination of transmission orreception by first server 6 at step S101. In the explanation of thisflowchart, it is attempted to communicate from first informationprocessor 1 to second information processor 2. Therefore, firstinformation processor 1 and first communication control unit 3 are attransmission side, and second information processor 2 and secondcommunication control unit 4 are at reception side. When attempted tocommunicate from second information processor 2 to first informationprocessor 1, the operation is same as explained in the flowchart below,except that first information processor 1 and first communicationcontrol unit 3, and second information processor 2 and secondcommunication control unit 4 are exchanged.

(Step S201) Characteristic determination unit 63 of first server 6determines characteristic of first communication control unit 3 attransmission side. Method of determination of characteristic isdescribed later.

(Step S202) Determination unit for transmitting and receiving 64 judgeswhether PS NAT is used or not in first communication control unit 3.When using PS NAT, the process goes to step S205, and if not using, theprocess goes to step S203.

(Step S203) Determination unit for transmitting and receiving 64 judgeswhether PR NAT is used or not in first communication control unit 3.When using PR NAT, the process goes to step S204, and if not using, thedetermination process of transmission or reception is over. That is,communication at step S102 is established by supposing first informationprocessor 1 and first communication control unit 3 to be at transmissionside, and second information processor 2 and second communicationcontrol unit 4 at reception side.

(Step S204) Determination unit for transmitting and receiving 64exchanges transmission and reception, and the determination process oftransmission and reception is over. That is, communication at step S102is established by supposing first information processor 1 and firstcommunication control unit 3 to be at reception side, and secondinformation processor 2 and second communication control unit 4 attransmission side.

(Step S205) Characteristic determination unit 63 determines thecharacteristic of second communication control unit 4 at reception side.

(Step S206) Determination unit for transmitting and receiving 64 judgeswhether PS NAT is used or not in second communication control unit 4.When using PS NAT, both transmission side and reception side are usingthe PS NAT, and communication cannot be established, and it is an error.If not using, the process goes to step S207.

(Step S207) Determination unit for transmitting and receiving 64 judgeswhether AS NAT is used or not in second communication control unit 4.When using AS NAT, the process goes to step S204, and if not using, thedetermination process of transmission or reception is over. That is,communication at step S102 is established by supposing first informationprocessor 1 and first communication control unit 3 to be at transmissionside, and second information processor 2 and second communicationcontrol unit 4 at reception side.

This flowchart is an example of determination of transmission andreception, and transmission or reception may be determined by othermethod. For example, in this flowchart, when PR NAT is used at thetransmission side, in order to save the number of times of determinationprocess, transmission and reception can exchanged without determiningthe type of NAT used at the reception side, but in the case the numberof times of determination process does not matter, after thetransmission side is determined to be using the PR NAT, it is determinedwhether the reception side is using PS NAT or AS NAT, and only wheneither one is determined to be used, transmission and reception mayexchanged.

Referring now to FIG. 7 to FIG. 9, the determination method ofcharacteristic of first communication control unit 3 is explained.Characteristic of second communication control unit 4 can be similarlydetermined.

In FIG. 7, information processor 1 transmits specified packet to portP101 of first server 6. Suppose this packet has passed through port 100of first communication control unit 3. The transmitted packet isreceived by characteristic determination unit 63 by way of communicationunit 61. In sequence, characteristic determination unit 63 transfers aninstruction of sending the packet to port P100 of first communicationcontrol unit 3 detecting by receiving this packet to communication unit71 of second server 7 by way of communication unit 61. Thus, the packetis sent from communication unit 71 to port P100. When first informationprocessor 1 can receive the packet to port P100 from communication unit71, characteristic determination unit 63 judges that full cone NAT isused in first communication control unit 3. On the other hand, whenfirst information processor 1 cannot receive the packet to port P100from communication unit 71, it is judged by the method explained in FIG.8.

In FIG. 8, information processor 1 transmits specified packet to portP101 and port P103 of first server 6, and port P102 of second server 7.The packet transmitted to port P101 and port P103 is received bycharacteristic determination unit 63, and the packet transmitted to portP102 is received by way of communication unit 71. It is judged whetherports Pa, Pb in first communication control unit 3 allowing to pass thepacket are the same or not. When port Pa and port Pb are different, itis judged that PS NAT is used in first communication control unit 3.

When port Pa and port Pb are the same, it is judged whether port Pb andport Pc are the same. When port Pb and port Pc are different, it isjudged that AS NAT is used in first communication control unit 3. Whenport Pa, port Pb and port Pc are the same, it is judged by the methodexplained in FIG. 9.

In FIG. 9, information processor 1 transmits specified packet to portP101 of first server 6. Receiving this packet, characteristicdetermination unit 63 sends a packet from port P103 different from portP101, to port P100 in first communication control unit 3 allowing topass this packet. When first information processor 1 can receive thepacket from port P103, characteristic determination unit 63 judges thatR NAT is used in first communication control unit 3, and when firstinformation processor 1 cannot receive the packet from port P103,characteristic determination unit 63 judges that PR NAT is used in firstcommunication control unit 3.

Thus, by the method explained in FIG. 7 to FIG. 9, characteristicdetermination unit 63 can judge the characteristic of firstcommunication control unit 3. In this explanation, although detail isomitted, transmission of packet or the like from first informationprocessor 1 is instructed by characteristic determination unit 63.

Process at step S102 in the flowchart in FIG. 5 is explained byreferring to FIG. 10. FIG. 10 is a diagram explaining the process ofexchanging information among sending side information processor, server,and receiving side information processor, about establishment ofcommunication. In FIG. 10, the server refers to both server 6 and server7. For the convenience of explanation, first information processor 1 andfirst communication control unit 3 are supposed to be at transmissionside, and second information processor 2 and second communicationcontrol unit 4 are at reception side.

(Step S301) Information transmitter and receiver 62 in first server 6sends address information showing IP address of second communicationcontrol unit 4 to first information processor 1. The sent addressinformation is received in communication unit 11 of first informationprocessor 1, and is transferred to bubble packet transmitter 12.

(Step S302) Target port transmitter for transmitting bubble packet 65sends the target port information for transmitting bubble packet tofirst information processor 1. The transmitted target port informationfor transmitting bubble packet is received in target port receiver fortransmitting bubble packet 16 through communication unit 11, and istransferred to bubble packet transmitter 12.

(Step S303) Port number differential detection packet transmitter 15 infirst information processor 1 sends the port number differentialdetecting packet to first server 6. In this transmission, ports of firstcommunication control unit 3 for passing plural port number differentialdetecting packets are mutually different. The port number differentialdetecting packets are transmitted from plural ports different in portnumber in, for example, first information processor 1. FIG. 11 is adiagram for explaining transmission of port number differentialdetecting packets. Port number differential detection packet transmitter15 sends port number differential detecting packets from different portsP205 to P208 sequentially to port P200 of first server 6. As a result,in first communication control unit 3, these packets pass throughdifferent ports P201 to P204. In FIG. 11, it is supposed to pass packetsin the sequence of ports P205 to P208. In first information processor 1,ports P205 to P208 are not used in communication with first server 6before transmission of port number differential detecting packets.

(Step S304) Port number differential detector 68 in first server 6receives the port number differential detecting packet sent from firstinformation processor 1, and detects the port number differential on thebasis of this port number differential detecting packet. Detectingmethod of port number differential is explained. Port numberdifferential detector 68 receives the port number differential detectingpacket, and detects the ports P201 to P204 of first communicationcontrol unit 3 used in transmission of each port number differentialdetecting packet. For example, in the case the port interval of portP202 and port P201 is 12, the port interval of port P203 and port P202is 6, and the port interval of port P204 and port P203 is 18, thesmallest port interval of 6 may be detected as port number differential.Or the greatest common measure of port intervals may be detected as portnumber differential. For example, in the case the port interval of portP202 and port P201 is 12, the port interval of port P203 and port P202is 6, and the port interval of port P204 and port P203 is 9, thegreatest common measure of 3 may be detected as port numberdifferential. The detected port number differential is transferred toport number differential information transmitter 69. Detecting method ofport number differential is not limited to these examples, but the portnumber differential may be detected by any other method. The number ofport number differential detecting packets used in transmission ofdetection of port number differential is not limited to 4, but may befreely changed within a range of detecting the port number differential.

(Step S305) Range detection packet transmitter 13 sends the rangedetecting packet to first server 6 by way of first communication controlunit 3. In this transmission, the packet is transmitted so as to passthe range detecting packet through the latest assigned port in firstcommunication control unit 3. This is intended to properly limit therange of ports including the bubble packet transmitting port. Forexample, range detection packet transmitter 13 sends the range detectingpacket by using a port of first information processor 1 not used so farin communication between first information processor 1 and first server6. Thus transmitted range detecting packet is received in range detector66 in first server 6. This range detector 66 refers to the port numberincluded in the header of received range detecting packet, and detectsthe position of the port of first communication control unit 3 used intransmission of range detecting packet.

(Step S306) Bubble packet transmitter 12 sends the bubble packet to thetarget port for transmitting bubble packet of second communicationcontrol unit 4 on the basis of the IP address of second communicationcontrol unit 4 indicated by address information sent at step S301 andthe target port information for transmitting bubble packet sent at stepS302. Herein, in the condition that communication is not established bytransmission of this bubble packet, the following steps are explained,but, for example, if full cone NAT is used in second communicationcontrol unit 4, and the target port for transmitting bubble packet hasbeen already used in second information processor 2, such as the portused in transmission or reception of information between secondinformation processor 2 and first server 6, the bubble packet isreceived in second information processor 2, and communication isestablished.

(Step S307) Range detection packet transmitter 13 sends the rangedetecting packet to second server 7 by way of first communicationcontrol unit 3. This range detecting packet is received in rangedetector 66 by way of communication unit 71 and communication unit 61.In the case of possibility of AS NAT being used in first communicationcontrol unit 3, it is required to send the range detecting packet tosecond server 7 in this manner, but if there is no possibility of AS NATbeing used in first communication control unit 3, the range detectingpacket after transmission of bubble packet may be also sent to firstserver 6. In this case, same as in step S305, the range detecting packetis transmitted or received by using, for example, a port of firstinformation processor 1 not used so-far in communication with firstserver 6. Thus transmitted range detecting packet is received in rangedetector 66 of first server 6. Range detector 66 detects the position ofthe port of first communication control unit 3 used in transmission ofrange detecting packet.

(Step S308) Range detector 66 detects the range of ports including thebubble packet transmitting port, on the basis of range detecting packetssent at step S305 and step S307. More specifically, ports including fromthe port of first communication control unit 3 used in transmission ofrange detecting packet at step S305, to the port of first communicationcontrol unit 3 used in transmission of range detecting packet at stepS307, are detected as range of ports including bubble packettransmitting port.

(Step S309) Range transmitter 67 sends the range information showing therange of ports including the bubble packet transmitting port detected byrange detector 66 to second information processor 2. This rangeinformation is received in range receiver 27 in second informationprocessor 2, and is transferred to reply packet transmitter 29.

(Step S310) Information transmitter and receiver 62 sends the addressinformation showing the IP address of first communication control unit 3to second information processor 2. The transmitted address informationis received in communication unit 21, and is transferred to reply packettransmitter 29.

(Step S311) Port number differential information transmitter 69 sendsthe port number differential information showing the port numberdifferential detected by port number differential detector 68 to secondinformation processor 2. The port number differential information isreceived in port number differential receiver 28 in second informationprocessor 2, and is transferred to reply packet transmitter 29.

(Step S312) Reply packet transmitter 29 sends a reply packet to firstcommunication control unit 3 specified by the IP address showing theaddress information received at step S310. The reply packet istransmitted at every port number differential showing the port numberdifferential information to the ports in the range indicted by the rangeinformation received from the range receiver 27.

(Step S313) Reply packet receiver 14 of first information processor 1receives the reply packet sent from second information processor 2. Byreceiving this reply packet, communication between first informationprocessor 1 and second information processor 2 is established.Consequently, between first information processor 1 and secondinformation processor 2, information is transmitted and received withoutresort to first server 6 or second server (that is, tunnelcommunication, etc.).

In FIG. 10, detection of port number differential (steps S303, S304) maybe anywhere before transmission of port number differential information(step S311), and, for example, the port number differential informationmay be sent to the reception side right after detection of port numberdifferential (step S304). Or transmission of address of transmissionside (step S310) may be simultaneous with transmission of address atreception side (step S301). Thus, in FIG. 10, there is a certain freedomabout sequence of process.

In transmission of reply packet, if reply packet is transmitted in everyport number differential indicated by port number differentialinformation, if the reply packet is not received (that is, if the noticeof reception of reply packet of second information processor 2 is notreceived from first information process 1 in a specified time aftertransmission of reply packet), it is possible that the detected portnumber differential is different, and in such a case, therefore, secondinformation processor 2 sets the port number differential to 1, andtries to send the reply packet again. Or if the port number differentialis calculated by the greater common measure, the common measures fromthe greatest common measure to 1 may be sequentially set in the portnumber differential, and the reply packet can be sent again. Forexample, if the detected port number differential is 8 or 4, thegreatest common measure of 4 is set as port number differential, and thereply packet is transmitted, and if the communication is not establishedyet, 2 is set as port number differential, and the reply packet may besent again. If still failing in communication, the port numberdifferential is set at 1.

Operation of communication system of the preferred embodiment isexplained by referring to specific examples. In the specific examples,IP addresses of first communication unit 3, second communication unit 4,first server 6 and second server 7 (as for first and secondcommunication control units 3 and 4, communication network 5 sideaddresses) are as follows.

First communication control unit 3: 202.132.10.6

Second communication control unit 4: 131.206.10.240

First server 6: 155.32.10.10

Second server 7: 155.32.10.20

It is supposed that connection is requested from first informationprocessor 1 to second information processor 2. That is, process isstarted in the condition that first information processor 1 is attransmission side.

Specifically, in example 1, AS NAT is used in first communicationcontrol unit 3, and PS NAT in second communication control unit 4. Inexample 2, PS NAT is used in first communication control unit 3, and ASNAT in second communication control unit 4. In example 3, PS NAT is usedin first communication control unit 3, and PR NAT in secondcommunication control unit 4. In example 4, full cone NAT is used inboth first communication control unit 3 and second communication controlunit 4.

EXAMPLE 1

FIG. 12 and FIG. 13 show example 1. First, operation of requestingconnection from first information processor 1 is explained. In FIG. 12,first information processor 1 has prior knowledge about IP address offirst server 6 (155.32.10.10) and IP address of second server 7(155.32.10.20), and sends device ID of first information processor 1(1234567890123456) to first server 6. This device ID is, for example,MAC address, EU164 base address, or other GUID (global unique ID). Thedevice ID is transmitted to port P3 of first server 6 by way of port P1of first communication control unit 3. By this transmission, informationtransmitter and receiver 62 of first server 6 acquires the device ID offirst information processor 1, IP address of first communication controlunit 3 (202.132.10.6) and port number (10130) of port P1 in firstcommunication control unit 3. These items of information are held ininformation transmitter and receiver 62.

Next, first information processor 1 sends the device ID(9876543210123456) of second information processor 2 for requestingconnection to first server 6, and requests connection to secondinformation processor 2. Information transmitter and receiver 62 offirst server 6 receives this connection request, and judges if secondinformation processor 2 has already accessed first server 6 or not.Access by second information processor 2 is also achieved by sendingdevice ID of second information processor 2 same as in the case of firstinformation processor 1. Therefore, if second information processor 2has already accessed first server 6, first server 6 has already acquiredthe device ID (9876543210123456) of second information processor 2, IPaddress (131.206.10.240) of second communication control unit 4, andport number (21000) of port P2 of second communication control unit 4used in transmission and reception of information between secondinformation processor 2 and first server 6, and these numbers are heldin information transmitter and receiver 62. If second informationprocessor 2 has already accessed first server 6, when informationtransmitter and receiver 62 transfers the instruction for determiningtransmission or reception to characteristic determination unit 63 (stepS101), and process of determination of transmission or reception isstarted. On the other hand, if second information processor 2 has notaccessed first server 6, connection request from first informationprocessor 1 is an error, and communication between first informationprocessor 1 and second information processor 2 is not established.

In determination of transmission or reception, characteristicdetermination unit 63 judges the characteristic of first communicationcontrol unit 3 which is the communication control unit at transmissionside (step S201). It is judged that AS NAT is used in firstcommunication control unit 3. This notice is transferred todetermination unit for transmitting and receiving 64. Determination unitfor transmitting and receiving 64 judges that PS NAT is not used, or PRNAT is not used in communication control unit at transmission side(steps S202, S203). As a result, transmission and reception are notexchanged, and the notice that first information processor 1 and firstcommunication control unit 3 are at transmission side and that secondinformation processor 2 and second communication control unit 4 are atreception side is transferred to information transmitter and receiver62, target port transmitter for transmitting bubble packet 65, rangetransmitter 67, and port number differential information transmitter 69.

Information transmitter and receiver 62, when receiving the notice thatfirst information processor 1 is at transmission side, sends the addressinformation showing IP address (131.206.10.240) of second communicationcontrol unit 4 at reception side to first information processor 1 by wayof port P1 (step S301). Target port transmitter for transmitting bubblepacket 65 sends the target port information for transmitting bubblepacket showing the port number (21000) of port P2 of secondcommunication control unit 4 to first information processor 1 by way ofport P1 (step S302).

In consequence, these items of information are received in communicationunit 11 of first information processor 1, and the address informationshowing the IP address (131.206.10.240) of second communication controlunit 4 is transferred to bubble packet transmitter 12, and the targetport information for transmitting bubble packet is transferred to targetport receiver for transmitting bubble packet 16. The target portinformation for transmitting bubble packet is received in target portreceiver for transmitting bubble packet 16, and transferred to bubblepacket transmitter 12. Thus, bubble packet transmitter 12 acquires theIP address of second communication control unit 4 as the destination oftransmission of bubble packet.

When communication unit 11 informs port number differential detectionpacket transmitter 15 of reception of target port information fortransmitting bubble packet, etc., port number differential detectionpacket transmitter 15 sends plural port number differential detectingpackets as shown in FIG. 11 (step S303). In FIG. 12 and FIG. 13,however, transmission of port number differential detecting packets isnot shown. The port number differential detecting packet is received inport number differential detector 68, and the port number differentialis detected. In this case, suppose the port number differential of 1 isdetected (step S304). The detected port number differential istransferred to port number differential information transmitter 69.

Bubble packet transmitter 12, before transmitting bubble packet,transfers the notice of transmission of range detecting packet to rangedetection packet transmitter 13. As a result, range detection packettransmitter 13, using a different port from the port use dincommunication with first server 6, transmits a range detecting packet tofirst server 6 (step S305). Herein, port P6 which is transmissiondestination port of the range detecting packet is supposed to beindicated from first server 6 to first information processor 1. Thisrange detecting packet is supposed to be transmitted by using port P5 offirst communication control unit 3. Receiving this range detectingpacket, range detector 66 detects port number (10135) of port P5 offirst communication control unit 3. Range detector 66 holds port number(10135) of port P5.

Range detection packet transmitter 13 informs bubble packet transmitter12 of transmission of range detecting packet after transmission of rangedetecting packet. As a result, bubble packet transmitter 12 sends thebubble packet to target port for transmitting bubble packet of portnumber (21000) in second communication control unit 4 of IP address(131.206.10.240) indicated by the address information received fromcommunication unit 11 (step S306). This bubble packet is supposed to betransmitted by using port P7 (port number 10142) of first communicationcontrol unit 3.

Bubble packet transmitter 12, after transmitting bubble packet, gives aninstruction of transmission of range detecting packet to range detectionpacket transmitter 13. As a result, range detection packet transmitter13 transmits the range detecting packet to second server 7 of which IPaddress is 155.32.10.20 (step S307). It is supposed that the bubblepacket and second range detecting packet are sent from the port of firstinformation processor 1 for transmitting the first range detectingpacket.

The range detecting packet sent after transmission of bubble packet issupposed to be transmitted by using port P8 of first communicationcontrol unit 3. Accordingly, range detector 66 detects port number(10145) of port P8 by receiving the range detecting packet by way ofcommunication unit 71 of second server 7 and communication unit 61 offirst server 6. In consequence, range detector 66 detects a rangespecified from port number (10135) of held port P5 and port number(10145) of detected port P8 as lower limit and upper limit, respectively(step S308). When this range is transferred to range transmitter 67,range transmitter 67 transmits range information showing the range tosecond information processor 2 by way of port P2 of second communicationcontrol unit 4 (step S309). This range information is received in rangereceiver 27 of second information processor 2, and is transferred toreply packet transmitter 29.

Ports P5, P7 and P8 are not consecutive port numbers, and this isbecause other devices (not shown) than first information processor 1 areconnected at the local side of first communication control unit 3, andports of first communication control unit 3 are assigned to such devicesuntil transmission of bubble packet from transmission of range detectingpacket, or until transmission of range detecting packet fromtransmission of bubble packet.

The notice of transmission of range information is transferred fromrange transmitter 67 to information transmitter and receiver 62 to portnumber differential information transmitter 69, information transmitterand receiver 62 sends the address information showing IP address(202.132.20.6) of first communication control unit 3 to secondinformation processor 2 (step S310). Port number differentialinformation transmitter 69 sends port number differential informationshowing port number differential detected by port number differentialdetector 68 to second information processor 2 (step S311). Consequently,the address information showing the IP address of first communicationcontrol unit 3 is transferred from communication unit 21 to reply packettransmitter 29, and port number differential information is transferredto port number differential receiver 28, and is transferred to replypacket transmitter 29. Thus, reply packet transmitter 29 acquires the IPaddress of first communication control unit 3 as transmissiondestination of reply packet.

Reply packet transmitter 29 sends reply packet to first communicationcontrol unit 3 of IP address (202.132.10.6) indicated by the addressinformation received from communication unit 21. This reply packet istransmitted, as shown in FIG. 13, from port number 10135 to 10145indicated by range information, in every port number differential 1 ofport number differential information. Herein, since PS NAT is used insecond communication control unit 4, the reply packet sent from secondinformation processor 2 is transmitted by using 11 ports from port P10to port P11 (step S312). In first communication control unit 3, sincethe transmission record is left in port P7 by transmission of bubblepacket, the reply packet sent to port P7 (port number 10142) out ofreply packets is transferred to first information processor 1, and isreceived in reply packet receiver 14 by way of communication unit 11(step S313). Thus, first information processor 1 acquires the positionof port of second communication control unit 4 used in transmission ofreply packet. Later, first information processor 1 transmits informationto this port through port P7 in first communication control unit 3, andcommunication between first information processor 1 and secondinformation processor 2 is established, and direct communication by UDPwithout resort to server is realized.

In this example 1, when the port number of bubble packet transmittingport (port P7) is 10140 and the port number differential of firstcommunication control unit 3 is 5, the reply packet is transmitted tothree ports only, that is, ports P5, P7, P8, so that the reply packetcan be transmitted efficiently.

Also in this example, second information processor 2 transmits the replypacket from the port (port of second information processor 2) forcommunicating with first server 6, but the reply packet may be alsotransmitted from other port. For example, in order that first server 6may detect the position of target port for transmitting bubble packet,the reply packet may be transmitted from the port of second informationprocessor 2 for transmitting the packet transmitted from secondinformation processor 2 to first server 6. In this case, the port ofsecond communication control unit 4 allowing to pass this packet is thetarget port for transmitting bubble packet.

In this example 1, the bubble packet and second range detecting packetare transmitted from the port of first information processor 1 fortransmitting the first range detecting packet, but the bubble packet andsecond range detecting packet may be also transmitted from mutuallydifferent ports newly assigned in first information processor 1.

EXAMPLE 2

In example 2, PS NAT is used in first communication control unit 3, andAS NAT is used in second communication control unit 4.

The operation of connection request from first information processor 1is same as in example 1, and its explanation is omitted.

Operation of determination of transmission or reception is explained.Characteristic determination unit 63 judges the characteristic of firstcommunication control unit 3 which is the communication control unit attransmission side (step S201). It is judged that PS NAT is used in firstcommunication control unit 3, and this notice is transferred todetermination unit for transmitting and receiving 64. Determination unitfor transmitting and receiving 64 judges that PS NAT is used incommunication control unit at transmission side (step S202), andtransfers the instruction of determination of characteristic of secondcommunication control unit 4 to characteristic determination unit 63.Characteristic determination unit 63 judges the characteristic of secondcommunication control unit 4 (step S205). It is judged that AS NAT isused in second communication control unit 4, and this notice istransferred to determination unit for transmitting and receiving 64.Determination unit for transmitting and receiving 64 judges that AS NATis used in communication control unit at reception side (steps S206,S207), and transmission and reception are exchanged (step S204).Therefore, first information processor 1 and first communication controlunit 3 are set at reception side, and second information processor 2 andsecond communication control unit 4 are set at transmission side. Thenotice that first information processor 1 and first communicationcontrol unit 3 are set at reception side, and that second informationprocessor 2 and second communication control unit 4 are set attransmission side is transferred to information transmitter and receiver62, target port transmitter for transmitting bubble packet 65, rangetransmitter 67, and port number differential information transmitter 69.The subsequent operation is same as in example 1 except that firstinformation processor 1 and second information processor 2 are exchangedand that the first communication control unit 3 and second communicationcontrol unit 4 are exchanged, and the explanation is omitted.

Meanwhile, the notice that first information processor 1 and firstcommunication control unit 3 are set at reception side, and that secondinformation processor 2 and second communication control unit 4 are setat transmission side is transferred to first information processor 1 orsecond information processor 2, or first information processor 1 orsecond information processor 2 may detect the transmission side whenreceiving the target port information for transmitting bubble packet,and detect the reception side when receiving the range information.

EXAMPLE 3

In example 3, PS NAT is used in first communication control unit 3, andPR NAT is used in second communication control unit 4.

The operation of connection request from first information processor 1is same as in example 1, and its explanation is omitted.

Operation of determination of transmission or reception is explained.Characteristic determination unit 63 judges the characteristic of firstcommunication control unit 3 which is the communication control unit attransmission side (step S201). It is judged that PS NAT is used in firstcommunication control unit 3, and this notice is transferred todetermination unit for transmitting and receiving 64. Determination unitfor transmitting and receiving 64 judges that PS NAT is used incommunication control unit at transmission side (step S202), andtransfers the instruction of determination of characteristic of secondcommunication control unit 4 to characteristic determination unit 63.Characteristic determination unit 63 judges the characteristic of secondcommunication control unit 4 (step S205). It is judged that PR NAT isused in second communication control unit 4, and this notice istransferred to determination unit for transmitting and receiving 64.Determination unit for transmitting and receiving 64 judges that PS NATis not used, or AS NAT is not used in communication control unit atreception side (steps S206, S207). As a result, transmission andreception are not exchanged, and the notice that first informationprocessor 1 and first communication control unit 3 are at transmissionside and that second information processor 2 and second communicationcontrol unit 4 are at reception side is transferred to informationtransmitter and receiver 62, target port transmitter for transmittingbubble packet 65, range transmitter 67, and port number differentialinformation transmitter 69.

Thereafter, the bubble packet and range detecting packet are transmittedfrom first information processor 1, and range information, IP address offirst communication control unit 3 and port number differentialinformation are received in second information processor 2, and thisoperation is same as in example 1, and its explanation is omitted.

FIG. 14 is a diagram explaining transmission of reply packet from secondinformation processor 2. In FIG. 14, reply packet transmitter 29 ofsecond information processor 2 sends the reply packet to port P5 of portnumber 10135 to port P8 of port number 10145 in first communicationcontrol unit 3 of IP address (202.132.10.6) on the basis of rangeinformation received in range receiver 27 from first server 6 (stepS312). The reply packet is transmitted in every port number differential1 indicated by port number differential information received in portnumber differential receiver 28. Since PR NAT is used in secondcommunication control unit 4, the reply packet is sent to firstcommunication control unit 3 by way of port P2. That is, the replypacket is sent from the port of second information processor 2 forcommunicating with first server 6. Other operation is same as in example1, and the explanation is omitted.

In this example 3, AS NAT is not used in first communication controlunit 3 at transmission side. Therefore, range detection packettransmitter 13 may receive this notice from characteristic determinationunit 63 or the like, and the range detecting packet after transmissionof bubble packet may be sent to first server 6, instead of second server7. In example 3, since PS NAT is used in first communication controlunit 3 at transmission side, when transmitting the range detectingpacket to first server 6, the port of first information processor 1 fortransmitting this packet may be same as the port used in communicationwith first server 6 by way of port 1. In this case, too, in order that anew port may be assigned in first communication control unit 3, it isnecessary to transmit the range detecting packet to port P3 differentfrom the port in first server 6, and port P6.

EXAMPLE 4

In example 4, full cone NAT is used in both first communication controlunit 3 and second communication control unit 4. Herein, only thecharacteristic points in this case are explained, and similar points tothe foregoing examples are not explained.

The operation of connection request from first information processor 1is same as in example 1, and its explanation is omitted.

In determination of transmission or reception, since full cone NAT isused in both communication control units, transmission and reception arenot exchanged, and first information processor 1 and first communicationcontrol unit 3 are determined at transmission side, and secondinformation processor 2 and second communication control unit 4 are atreception side.

Transmission of bubble packet and others is explained briefly byreferring to FIG. 15 and FIG. 16. In FIG. 15, when full cone NAT is usedin first communication control unit 3, range detecting packet and bubblepacket are transmitted by using same port P5. Hence, only one bubblepacket transmitting port is specified by range information. Accordingly,as shown in FIG. 16, the reply packet sent from second informationprocessor 2 is sent to port P5 by way of port P2, and communicationbetween first information processor 1 and second information processor 2can be established.

This explanation is intended to conform to the processing flow in FIG.10, but when full cone NAT is used in second communication control unit4, the transmitted bubble packet can be received in second informationprocessor 2, and hence communication is established at this point.Therefore it is not necessary to transmit range detecting packet ortransmit reply packet.

In the foregoing examples, the transmission destination of bubble packetis port P2 (the port used in communication with first server 6 by secondinformation processor 2), which is because communication can beestablished if PR NAT or PS NAT is used in first communication controlunit 3 at transmission side, and full cone NAT, R NAT, or PR NAT is usedin second communication control unit 4 at reception side. Therefore, inother cases (for example, in the case of example 4), the bubble packetmay be transmitted to other than port P2. In particular, when full coneNAT is used in first communication control unit 3, the bubble packet maybe transmitted to other device than second communication control unit 4.

When first communication control unit 3 at transmission side is usingother than AS NAT, the range detecting packet to be transmitted tosecond server 7 may be transmitted to first server 6.

The range detecting packet to be transmitted before and aftertransmission of bubble packet may be sent to first server 6 by using aport newly assigned in first information processor 1 individually. Inthis manner, in every transmission of range detecting packet, a new portis assigned in first communication control unit 3, and the range ofports including the bubble packet transmitting port can be detected.Therefore, even if AS NAT is used in first communication control unit 3at transmission side, without using second server 7, the range of portsincluding the bubble packet transmitting packet can be detected.Meanwhile, when the bubble packet and the range detecting packet aretransmitted from different ports in first information processor 1, theport of first communication control unit 3 allowing to pass the rangedetecting packet, and the port of first communication control unit 3allowing to pass the bubble packet are different. Therefore, in such acase, the end of range for transmitting the reply packet may bedetermined at the position of the port closer to the bubble packettransmitting port by one port number differential than the port (port infirst communication control unit 3) for allowing to pass the rangedetecting packet transmitted from the port different from the port (portin first information processor 1) transmitting the bubble packet. Whentransmitting the range detecting packet two times, the port fortransmitting one range detecting packet (port in first informationprocessor 1) may be same as the port for transmitting the bubble packet.In such a case, the range of ports including the bubble porttransmitting port includes the port of first communication control unit3 allowing to pass the range detecting packet transmitted from the sameport as the port for transmitting the bubble packet (port in firstinformation processor 1).

Further, when first communication control unit 3 at transmission sideuses any one of full cone NAT, R NAT, and PR NAT, it is enough to sendthe range detecting packet only either before or after transmitting thebubble packet. That is, when first communication control unit 3 useseither R NAT or PR NAT, too, if the bubble packet and range detectingpacket are sent from same port of first information processor 1, asshown in FIG. 15, port P5, port P7, and port P8 are same port, and byone range detecting packet, the bubble packet transmitting port can beidentified. Further, when first communication control unit 3 attransmission side transmits bubble packet by way of a port forcommunicating with, for example, first server 6 (for example, port P1 inFIG. 15), it is not required to transmit range detecting packet.

FIG. 17 relates to types of NAT used in communication control unit,showing whether connectable or not. In the communication system of thepreferred embodiment, unless PS NAT is used in both first communicationcontrol unit 3 and second communication control unit 4, firstinformation processor 1 and second information processor 2 can beconnected. In the foregoing explanation of examples, exceptionalhandling depending on the type of NAT used in the communication controlunit is also described, but regardless of the type of NAT used in thecommunication control unit, by transmitting the range detecting packetbefore bubble packet transmission and the range detecting packet afterbubble packet transmission to different addresses, and specifying theport of transmission destination of bubble packet as the port used intransmission and reception of information by the information processorat reception side with the server, and transmitting the reply packet tothe range of ports including the bubble packet transmitting portdetected by using the range detecting packet, the information processorscan be connected in the combination indicated by ◯-mark in FIG. 17. Asfor combination of Δ-mark in FIG. 17, the information processors can beconnected by exchanging transmission and reception.

Herein, when PS NAT is used at transmission side and PS NAT or AS NAT isused at reception side, or PR NAT is used at transmission side and ASNAT or PS NAT is used at reception side, communication betweeninformation processors cannot be established, and the reason is brieflyexplained by referring to FIG. 12 to FIG. 14.

(1) In the Case of PS NAT Used at Transmission Side, and PS NAT or ASNAT at Reception Side

In this case, since PS NAT is used in first communication control unit3, supposing the bubble packet to be transmitted to port P2, firstinformation processor 1 can receive only the reply packet transmittedfrom its port P2. On the other hand, second communication control unit 4is using PS NAT or AS NAT, and second communication control unit 4 isusing port P2 for communicating with first server 6, and hence secondinformation processor 2 cannot transmit reply packet to firstcommunication control unit 3 by way of port P2 (that is, reply packetcannot be transmitted as shown in FIG. 14). In this case, therefore,communication cannot be established. However, unless PS NAT is used atboth transmission side and reception side, communication can beestablished by exchanging the transmission side and reception side.

(2) In the Case of PR NAT Used at Transmission Side, and PS NAT or ASNAT at Reception Side

In this case, same as in case (1), since PR NAT is used in firstcommunication control unit 3, supposing to transmit bubble packet toport P2, first information processor 1 can receive only the reply packettransmitted from its port P2. On the other hand, second communicationcontrol unit is using AS NAT or PS NAT, and hence reply packet cannot bereplied through port P2. In this case, therefore, communication cannotbe established. As mentioned above, however, in this case, ports P5, P7,P8 in first communication control unit 3 are the same port. In thiscase, too, communication can be established by exchanging thetransmission side and reception side.

Thus, in the communication system of the preferred embodiment, exceptwhen PS NAT is used in both first communication control unit 3 andsecond communication control unit 4, communication can be establishedbetween first information processor 1 and second information processor2.

Preferred Embodiment 2

A communication system in preferred embodiment 2 of the invention isdescribed while referring to the accompanying drawings. Thecommunication system in the preferred embodiment is intended to lessenthe processing load of the server by detecting the range of portsincluding the bubble packet transmitting port or detecting the portnumber differential not in the server but in the information processor.

The configuration of the communication system in the preferredembodiment is same as shown in FIG. 1, except that first informationprocessor 10, second information processor 20, and first server 60 areprovided instead of first information processor 1, second informationprocessor 2, and first server 6, and the detailed description isomitted.

FIG. 18 is a block diagram of configuration of first informationprocessor 10 in the preferred embodiment. In FIG. 18, first informationprocessor 10 comprises communication unit 11, bubble packet transmitter12, range detection packet transmitter 13, reply packet receiver 14,port number differential detection packet transmitter 15, target portreceiver for transmitting bubble packet 16, range receiver 17, portnumber differential receiver 18, reply packet transmitter 19, portinformation receiver for detecting 71, range detector 72, rangetransmitter 73, port number differential information receiver 74, portnumber differential detector 75, and port number differentialinformation transmitter 76. Structure and operation of other componentsthan port information receiver for detecting 71, range detector 72,range transmitter 73, port number differential information receiver 74,port number differential detector 75, and port number differentialinformation transmitter 76 are same as shown in preferred embodiment 1,except that port number differential receiver 18 receives the portnumber differential information transmitted from second informationprocessor 20 by way of first server 60, and the explanation is omitted.

Port information receiver for detecting 71 receives the port informationfor detecting transmitted from first server 60 by way of communicationunit 11. The port information for detecting is the information showingthe position of the port of first communication control unit 3 allowingto pass the range detection packet transmitted by range detection packettransmitter 13.

Range detector 72 detects the range of ports including the bubble packettransmitting port, on the basis of the port information for detectingreceived in port information receiver for detecting 71. The range ofports may be detected by acquiring the port number included in thepayload of the packet of port information for detecting, and recordingin specified memory or the like.

Range transmitter 73 transmits the range information which is theinformation showing the range of ports including the bubble packettransmitting port detected by range detector 72, to second informationprocessor 20 by way of first server 60.

Port number differential information receiver 74 receives the portinformation for detecting port number differential. The port informationfor detecting port number differential is the information showing theposition of the port of first communication control unit 3 allowing topass the port number differential packet transmitted by port numberdifferential detection packet transmitter 15. This port information fordetecting port number differential is transmitted from first server 60.

Port number differential detector 75 detects the port numberdifferential in first communication control unit 3, on the basis of portinformation for detecting port number differential received in portinformation for detecting port number differential 74. The port numberdifferential is detected same as in port number differential detector 68in preferred embodiment 1, and its explanation is omitted.

Port number differential information transmitter 76 transmits the portnumber differential information which is the information showing theport number differential of first communication control unit 3 detectedby port number differential detector 75, to second information processor20 by way of first server 60.

The components from bubble packet transmitter 12 to target port receiverfor transmitting bubble packet 16 and from port information receiver fordetecting 71 to port number differential information transmitter 76 infirst information processor 10 are used when first information processor10 operates at transmission side. The components from range receiver 17to reply packet transmitter 19 are used when first information processor10 operates at reception side.

FIG. 19 is a block diagram of configuration of second informationprocessor 20 in the preferred embodiment. In FIG. 19, second informationprocessor 20 comprises communication unit 21, bubble packet transmitter22, range detection packet transmitter 23, reply packet receiver 24,port number differential detection packet transmitter 25, target portreceiver for transmitting bubble packet 26, range receiver 27, portnumber differential receiver 28, reply packet transmitter 29, portinformation receiver for detecting 81, range detector 82, rangetransmitter 83, port number differential information receiver 84, portnumber differential detector 85, and port number differentialinformation transmitter 86. Herein, the components from communicationunit 21 to port number differential information transmitter 86 in secondinformation processor 20 are same as communication unit 11 to portnumber differential information transmitter 76 in first informationprocessor 10, except that first information processor 10, firstcommunication control unit 3, second information processor 20, andsecond communication control unit 4 are exchanged, and detaileddescription is omitted.

The components from bubble packet transmitter 22 to target port receiverfor transmitting bubble packet 26 and from port information receiver fordetecting 81 to port number differential information transmitter 86 insecond information processor 20 are used when second informationprocessor 20 operates at transmission side. The components from rangereceiver 27 to reply packet transmitter 29 are used when secondinformation processor 20 operates at reception side.

FIG. 20 is a block diagram of configuration of first server 60 in thepreferred embodiment. In FIG. 20, first server 60 comprisescommunication unit 61, information transmitter and receiver 62,characteristic determination unit 63, determination unit fortransmitting and receiving 64, target port transmitter for transmittingbubble packet 65, detector for detecting port number 91, port numberinformation transmitter for detecting port number 92, port numberdifferential information detector 93, and port number informationtransmitter for detecting port number 94. Structure and operation otherthan detector for detecting port number 91, port number informationtransmitter for detecting port number 92, port number differentialinformation detector 93, and port number information transmitter fordetecting port number 94 are same as in preferred embodiment 1, and theexplanation is omitted.

Detector for detecting port number 91 receives the range detectionpacket sent from the transmission side information processor, anddetects the position of the port of the transmission side communicationcontrol unit allowing to pass the range detection packet on the basis ofthe range detection packet. The port position is detected by acquiringthe position of the port of the transmission side communication controlunit allowing to pass the range detection packet included in the rangedetection packet (for example, included in the header of range detectionpacket). The range detection packet may be one sent from thetransmission side information processor to communication unit 61, or maybe other sent to communication unit 71 of second server 7, and receivedby way of communication unit 61. In the latter case, IP addresses shouldbe different in first server 60 and second server 7.

Port number information transmitter for detecting port number 92transmits the port information for detecting showing the position of theport detected by detector for detecting port number 91 to thetransmission side information processor.

Port number differential information detector 93 receives the portnumber differential detection packet sent from the transmission sideinformation processor by way of transmission side communication controlunit, and detects the position of the port of the transmission sidecommunication control unit allowing to pass the port number differentialdetection packet on the basis of the port number differential detectionpacket.

Port number information transmitter for detecting port number 94transmits the port number differential detection port informationshowing the position of the port of transmission side communicationcontrol unit allowing to pass the port number differential detectionpacket detected by port number differential information detector 93, tothe transmission side information processor.

The operation of communication system of the preferred embodiment isexplained. The operation of the communication system in the preferredembodiment is same as the operation in preferred embodiment 1 shown inFIG. 5, except that the range of ports including the bubble packettransmitting port is detected or the port number differential isdetected by first information processor 10 and second informationprocessor 20, and the explanation is omitted.

In the flowchart in FIG. 5, the process at step S102 is explained byreferring to FIG. 21 to FIG. 23. FIG. 21 to FIG. 23 are diagrams forexplaining the exchange and processing of information among thetransmission side, servers, and reception side. The server in FIG. 21 toFIG. 23 refers to both server 60 and server 7. For the convenience ofexplanation, first information processor 10 and first communicationcontrol unit 3 are supposed to be at transmission side, and secondinformation processor 20 and second communication control unit 4 aresupposed to be at transmission side. Process at steps S301 to S303, S305to S307, S310, S312, and S313 is same as explained in FIG. 10 inpreferred embodiment 1, and the explanation is omitted.

(Step S401) Port number differential information detector 93 of firstserver 60 receives a port number differential detection packettransmitted from first information processor 10. Port numberdifferential information detector 93 detects the position of the port offirst communication control unit 3 allowing to pass this port numberdifferential detection packet.

(Step S402) Port number information transmitter for detecting portnumber 94 transmits the port differential information which is theinformation showing the position of the port of first communicationcontrol unit 3 allowing to pass the port number differential detectionpacket detected by port number differential information detector 93, tofirst information processor 10. This port differential information isreceived in port number differential information receiver 74 in firstinformation processor 10.

(Step S403) Port number differential detector 75 detects the port numberdifferential of first communication control unit 3 on the basis of portdifferential information received in port number differentialinformation receiver 74. This detection of port number differential issame as in preferred embodiment 1, and its explanation is omitted.

(Step S404) Detector for detecting port number 91 of first server 60receives a range detection packet sent from first information processor10. Detector for detecting port number 91 detects the position of portin first communication control unit 3 allowing to pass this portdetection packet included in the header of range detection packet.

(Step S405) Port number information transmitter for detecting portnumber 92 transmits the port number information showing the position ofthe port of first communication control unit 3 allowing to pass therange detection packet detected by detector for detecting port number91, to first information processor 10. This port number information isreceived in port differential information receiver 71 in firstinformation processor 10.

(Step S406) Detector for detecting port number 91 of first server 60receives a range detection packet transmitted from first informationprocessor 10. Detector for detecting port number 91 detects the positionof port of first communication control unit 3 allowing to pass this portdetection packet included in the header of range detection packet.

(Step S407) Port number information transmitter for detecting portnumber 92 transmits the port number information showing the position ofthe port of first communication control unit 3 allowing to pass therange detection packet detected by detector for detecting port number91, to first information processor 10. This port number information isreceived in port differential information receiver 71 in firstinformation processor 10.

(Step S408) Range detector 72 of first information processor 10 acquiresthe position of the port of first information processor 3 allowing topass the range detection packet transmitted at steps S305, S307, fromthe port number information received in port differential informationreceiver 71, and detects the range of ports covering the two ports atboth ends.

(Step S409) Range transmitter 73 of first information processor 10transmits the range information which is the information showing therange of ports detected at step S408, to first server 60 together withinstruction for transmitting the range information to second informationprocessor 20.

(Step S410) Communication unit 61 of first server 60 receives the rangeinformation, and transmits this range information to second informationprocessor 20. This range information is received in range receiver 27 insecond information processor 20.

(Step S411) Port number differential information transmitter 76transmits the port differential information showing the port numberdifferential of first communication control unit 3 detected at stepS403, to first server 60 together with instruction for transmitting thisport differential information to second information processor 20.

(Step S412) Communication unit 61 of first server 60 receives the portdifferential information, and transmits this port differentialinformation to second information processor 20. This range informationis received in port number differential receiver 28 in secondinformation processor 20.

In FIG. 21 to FIG. 23, there is a certain freedom about sequence ofprocess same as in FIG. 10. For example, address transmission attransmission side (step S310) may be done at the same time as addresstransmission at reception side (step S301). In particular, in FIG. 22,transmission of range detection packet and transmission of bubble packet(steps S305 to S307) may be done without waiting for reception ofdetection port information. However, the range is detected (step S408)after reception of port number information.

In specific examples of operation of communication system of thepreferred embodiment, the port number differential in transmission sidecommunication control unit is detected in the transmission sideinformation processor, and the range of ports including the bubblepacket transmission port is detected in the transmission sideinformation processor, and accompanying processes are done (for example,transmission of range information from first information processor 10 tosecond information processor), and other operations are same as inpreferred embodiment 1, and the explanation is omitted.

Hence, in the communication system in the preferred embodiment, inaddition to the same effects as in preferred embodiment 1, detection ofport number differential in first communication control unit 3 or secondcommunication control unit 4, or detection of range including ports ofbubble packet transmitting port can be done in first informationprocessor 10 or second information processor 20, so that the processingload in first server 60 can be saved. In particular, since theprocessing load is very in waiting process (such as process of waitingfor transmission of second range detection packet after transmission offirst range detection packet), such waiting process is not done in theserver, so that the processing load of first server 60 may besubstantially lessened.

In this preferred embodiment, detection of port number differential ofcommunication control unit, or detection of range including ports ofbubble packet transmitting port is done in first information processor,but either process may be done in the server same as in preferredembodiment 1.

In the preferred embodiment, the characteristic of communication controlunit is determined by the server, but the characteristic ofcommunication control unit may be determined also in the informationprocessor. In this case, too, by transmitting the information showingthe position of the port of communication control unit allowing to passthe packet transmitted from the information processor from the server tothe information processor, the characteristic of communication controlunit can be determined in the information processor same as in preferredembodiment 1.

Preferred Embodiment 3

A communication system in preferred embodiment 3 of the invention isdescribed while referring to the accompanying drawings. Thecommunication system in the preferred embodiment is characterized bythat one information processor communicates directly without resort tocommunication control unit.

FIG. 24 is a block diagram of configuration of communication system inthe preferred embodiment. In FIG. 24, the communication system in thepreferred embodiment comprises first information processor 1, secondinformation processor 2, first communication control unit 3, firstserver 6, and second server 7. The communication system in the preferredembodiment shown in FIG. 24 is same as the communication system inpreferred embodiment 1, except that second communication control unit isnot provided. The structure and operation of first information processor1, second information processor 2, first server 6, and second server 7are same as in preferred embodiment, and the detailed description isomitted.

Herein, since second information processor 2 is intended to communicatewithout resort to communication control unit, second informationprocessor 2 is assumed to be communication as if by way of communicationcontrol unit of full cone NAT. Therefore, the operation in thispreferred embodiment is same as operation in the case of secondcommunication control unit 4 operating on full cone NAT in preferredembodiment 1, and communication between first information processor 1and second information processor 2 can be established.

Thus, in the communication system of the preferred embodiment, if secondinformation processor 2 communicates without resort to communicationcontrol unit, communication between first information processor 1 andsecond information processor 2 can be established.

This preferred embodiment is similar to the communication system inpreferred embodiment 1 except that second communication control unit isnot provided, but it is similarly realized in the communication systemin preferred embodiment 2 excluding second communication control unit.Thus, if the second information processor communicates without resort tocommunication control unit, communication between first informationprocessor 1 and second information processor 2 can be established.

Or, in the preferred embodiment, second information processor 2communicates without resort to communication control unit, but if secondinformation processor 2 communicates by way of communication controlunit, and first information processor 1 communicates without resort tocommunication control unit, similarly, communication between firstinformation processor 1 and second information processor 2 can beestablished.

In the explanation of the foregoing preferred embodiments, whendetermining the transmission side and reception side of informationprocessor and communication control unit, first the informationprocessor is provisionally determined as transmission side, and it isexplained to exchange later depending on the characteristic of thecommunication control unit, but when first server 6 or the like receivesthe request for establishment of communication with other informationprocessor from the information processor, the characteristic of firstcommunication control unit 3 and second communication control unit 4 canbe determined, and depending on the result of determination ofcharacteristic, the information processor at transmission side andinformation processor at reception side can be determined (in this case,there is no concept of “exchange of transmission and reception”).

Preferred Embodiment 4

A communication system in preferred embodiment 4 of the invention isdescribed while referring to the accompanying drawings. Thecommunication system in the preferred embodiment is intended to transmitone or more bubble packets.

FIG. 25 is a block diagram of configuration of communication system inthe preferred embodiment. In FIG. 25, the communication system in thepreferred embodiment comprises first information processor 30, secondinformation processor 40, first communication control unit 3, secondcommunication control unit 4, and second server 50. First communicationcontrol unit 3 and second communication control unit 4 are same as inpreferred embodiment 1, and the explanation is omitted.

FIG. 26 is a block diagram of configuration of first informationprocessor 30 in the preferred embodiment. In FIG. 26, first informationprocessor 30 comprises communication unit 11, bubble packet transmitter12, range detection packet transmitter 13, reply packet receiver 14,port number differential detection packet transmitter 15, target portreceiver for transmitting bubble packet 16, range receiver 17, portnumber differential receiver 18, reply packet transmitter 19, portinformation receiver for detecting 71, range detector 72, rangetransmitter 73, port number differential information receiver 74, portnumber differential detector 75, port number differential informationtransmitter 76, port assigning packet transmitter 31, target porttransmitter for transmitting bubble packet 32, characteristicdetermination unit 33, and characteristic transmitter 34. Structure andoperation of other components than port assigning packet transmitter 31,target port transmitter for transmitting bubble packet 32,characteristic determination unit 33, and characteristic transmitter 34are same as shown in preferred embodiment 2, except that bubble packettransmitter 12 transmits one or more bubble packets, and that portdifferential information receiver 71 and range detector 72 areresponsible for process of detection of range about the bubble packettransmitting port and process of detection of range about port assigningpacket transmitted by port assigning packet transmitter 31 describedbelow, and the explanation is omitted.

Port assigning packet transmitter 31 transmits a port assigning packetfor assigning the packet for transmitted a reply packet in firstcommunication control unit 3. This port assigning packet is transmittedto second communication control unit 4. The port in second communicationcontrol unit 4 to which the port assigning packet is transmitted isarbitrary. For example, the port assigning packet is transmitted to theport of second communication control unit 4 used in communication withserver 50 by second information processor 40. Reply packet transmitter19 is to transmit reply packet from the port of first informationprocessor 30 transmitting the port assigning packet from this portassigning packet transmitter 31.

Target port transmitter for transmitting bubble packet 32 transmits therange of one or more ports including the port (called port assigningpacket transmitting port) of first communication control unit 3 allowingto pass port assigning packet transmitter 31 detected by range detector72, to second information processor 40 by way of server 50, as targetport information for transmitting bubble packet.

Characteristic determination unit 33 determines the characteristic offirst communication control unit 3. More specifically, transmitting thecharacteristic determination packet to server 50, the characteristicdetermination packet information which is the information showing theposition of the port of first communication control unit 3 allowing topass this characteristic determination packet is received, and thecharacteristic of first communication control unit 3 is determined.

Characteristic transmitter 34 sends the characteristic information whichis the information showing the characteristic of first communicationcontrol unit 3 determined by characteristic determination unit 33 tosecond information processor 40 by way of server 50.

In the preferred embodiment, the components from bubble packettransmitter 12 to target port receiver for transmitting bubble packet 16and from port information receiver for detecting 71 to port numberdifferential information transmitter 76 in first information processor30 are used when first information processor 30 operates at transmissionside. The components from range receiver 17 to reply packet transmitter19, and range detection packet transmitter 13, port assigning packettransmitter 31, target port transmitter for transmitting bubble packet32, and port information receiver for detecting 71 to port numberdifferential information transmitter 76 are used when first informationprocessor 30 operates at reception side. In other words, range detectionpacket transmitter 13, and port information receiver for detecting 71 toport number differential information transmitter 76 are used when firstinformation processor 30 operates at both transmission side andreception side. The preferred embodiment is explained when thecomponents of range detection packet transmitter 13, and portinformation receiver for detecting 71 to port number differentialinformation transmitter 76 are used when first information processor 30operates at both transmission side and reception side, but one or morecomponents of these components may be provided independently when firstinformation processor 30 operates at transmission side, and at receptionside.

FIG. 27 is a block diagram of configuration of second informationprocessor 40 in the preferred embodiment. In FIG. 27, second informationprocessor 40 comprises communication unit 21, bubble packet transmitter22, range detection packet transmitter 23, reply packet receiver 24,port number differential detection packet transmitter 25, target portreceiver for transmitting bubble packet 26, range receiver 27, portnumber differential receiver 28, reply packet transmitter 29, portinformation receiver for detecting 81, range detector 82, rangetransmitter 83, port number differential information receiver 84, portnumber differential detector 85, port number differential informationtransmitter 86, port assigning packet transmitter 41, target porttransmitter for transmitting bubble packet 42, characteristicdetermination unit 43, and characteristic transmitter 44. In secondinformation processor 40, the components from communication unit 21 toport number differential information transmitter 86 are same ascommunication unit 11 to port number differential informationtransmitter 76 in first information processor 30 except that firstinformation processor 30, first communication control unit 3, secondinformation processor 40, and second communication control unit 4 areexchanged, and the explanation is omitted.

In the preferred embodiment, the components from bubble packettransmitter 22 to target port receiver for transmitting bubble packet 26and from port information receiver for detecting 81 to port numberdifferential information transmitter 86 in second information processor40 are used when second information processor 40 operates attransmission side. The components from range receiver 27 to reply packettransmitter 29, and range detection packet transmitter 23, portassigning packet transmitter 41, target port transmitter fortransmitting bubble packet 42, and port information receiver fordetecting 81 to port number differential information transmitter 86 areused when second information processor 40 operates at reception side.That is, range detection packet transmitter 23, and port differentialinformation receiver 81 to port number differential detector 86 are usedin both cases of second information processor 40 used at transmissionside and at reception side. Also, in the preferred embodiment, it isexplained when the components of range detection packet transmitter 23,and port information receiver for detecting 81 to port numberdifferential information transmitter 86 are used when second informationprocessor 40 operates at both transmission side and reception side, butone or more components of these components may be provided independentlywhen second information processor 40 operates at transmission side, andat reception side.

FIG. 28 is a block diagram of configuration of server 50 in thepreferred embodiment. In FIG. 28, server 50 comprises communication unit61, information transmitter and receiver 62, target port transmitter fortransmitting bubble packet 65, detector for detecting port number 91,port number information transmitter for detecting port number 92, portnumber differential information detector 93, port number informationtransmitter for detecting port number 94, port detector forcharacteristic determination 95, port information transmitter forcharacteristic determination 96, and target port receiver fortransmitting bubble packet 97. Structure and operation other than portdetector for characteristic determination 95, port informationtransmitter for characteristic determination 96, and target portreceiver for transmitting bubble packet 97 in server 50 are same as inpreferred embodiment 2, except that detector for detecting port number91, port number information transmitter for detecting port number 92,port number differential information detector 93, and port numberinformation transmitter for detecting port number 94 are active in bothinformation processor at transmission side and information processor atreception side, and the explanation is omitted. In the preferredembodiment, target port transmitter for transmitting bubble packet 65 isto transmit the target port information of bubble packet received intarget port receiver for transmitting bubble packet 97.

Port detector for characteristic determination 95 receives packet forcharacteristic determination transmitted from first informationprocessor 30 or second information processor 40, and detects theposition of the port of first communication control unit 3 or secondcommunication control unit 4 allowing to pass the packet forcharacteristic determination on the basis of this packet forcharacteristic determination. The port position is detected by acquiringthe position of the port of first communication control unit 3 or secondcommunication control unit 4 allowing to pass the packet forcharacteristic determination included in the packet for characteristicdetermination (for example, included in the header of packet forcharacteristic determination).

Port information transmitter for characteristic determination 96transmits the port information for characteristic determination showingthe position of the port detected by port detector for characteristicdetermination 95, to the information processor having transmitted thepacket for characteristic determination.

Target port receiver for transmitting bubble packet 97 receives thetarget port information for transmitting bubble packet which is theinformation showing the target port for transmitting bubble packet. Thetarget port for transmitting bubble packet indicated by this target portinformation for transmitting bubble packet is one or more ports.

The operation of communication system of the preferred embodiment isexplained. The operation of the communication system in the preferredembodiment is same as the operation in preferred embodiment 1 shown inFIG. 5, and the explanation is omitted.

In the flowchart in FIG. 5, the process at step S101 is explained byreferring to FIG. 29. FIG. 29 is a flowchart of process of determinationof transmission side and determination side of information processor. Inthis explanation of flowchart, it is supposed that second informationprocessor 40 is attempting to communicate with first informationprocessor 30. Therefore, first information processor 30 and firstcommunication control unit 3 are at receiving side, and secondinformation processor 40 and second communication control unit 4 are atsending/calling side. Alternatively, if first information processor 30attempts to call second information processor 40, only first informationprocessor 30 and first communication control unit 3, and secondinformation processor 40 and second communication control unit 4 areexchanged, and other points are same as in the flowchart. Thesending/calling side is the side requesting communication with thepartner side, and the receiving side is the side requested tocommunicate from the sending/calling side.

(Step S501) Characteristic determination unit 43 of second informationprocessor 40 determines the characteristic of second communicationcontrol unit 4, that is, communication control unit at sending/callingside. Method of determining the characteristic is described below.

(Step S502) Characteristic determination unit 43 judges if PS NAT isused or not in second communication control unit 4. When PS NAT is used,characteristic transmitter 44 send the characteristic informationshowing PS NAT is used in second communication control unit 4 to firstinformation processor 30 by way of server 50, and the process goes tostep S504, and otherwise the process goes to step S503.

(Step S503) Characteristic determination unit 43 determines thesending/calling side device, that is, second information processor 40 asthe reception side device, that is, the device at the side of receivingthe bubble packet. This ends the process of determination oftransmission and reception.

(Step S504) Characteristic determination unit 33 of first informationprocessor 30 determines the characteristic of first communicationcontrol unit 3 which is the communication control unit at receivingside. Method of determining the characteristic is described below.

(Step S505) Characteristic determination unit 33 judges if PS NAT isused or not in first communication control unit 3. When PS NAT is used,both transmission side and reception side are using PS NAT, and it is anerror. If PS NAT is not used, the process goes to step S506.

(Step S506) Characteristic determination unit 33 determines thereceiving side device, that is, first information processor 30 as thereception side device, that is, the device at the side of receiving thebubble packet. This ends the process of determination of transmissionand reception.

Referring now to FIG. 30, the method of determining the characteristicof first communication control unit 3 is explained. The characteristicof second communication control unit 4 can be similarly determined.

In FIG. 30, characteristic determination unit 33 of first informationprocessor 30 transmits two characteristic determination packets to portP300 and port P301 of server 50 from one port P100. Herein, port P300and port P301 are different ports. Port detector for characteristicdetermination 95 of server 50 detects the position of ports (P200, P201)of first communication control unit 3 allowing to pass each packet forcharacteristic determination transmitted to ports P300, P301. The portinformation for characteristic determination as the information showingthe port position is transmitted from port information transmitter forcharacteristic determination 96 to first information processor 30. Then,characteristic determination unit 33 receives this port information forcharacteristic determination, and judges the characteristic of firstcommunication control unit 3 depending on whether or not port P200 andport P201 are identical. More specifically, if port P200 and port P201are identical, it is judged that PS NAT is not used in firstcommunication control unit 3. On the other hand, if port P200 and portP201 are different, it is judged that PS NAT is used in firstcommunication control unit 3.

The process at step S102 in the flowchart in FIG. 5 is explained byreferring to FIG. 31 to FIG. 33. FIG. 31 to FIG. 33 are diagrams forexplaining the exchange and processing of information among thetransmission side information processor, server, and reception sideinformation processor, about establishment of communication. For theconvenience of explanation, first information processor 30 and firstcommunication control unit 3 are supposed to be at transmission side,and second information processor 40 and second communication controlunit 4 are supposed to be at transmission side.

(Step S601) Information transmitter and receiver 62 of server 50transmits the address information showing the IP address of firstcommunication control unit 3 to second information processor 40. Thetransmitted address information is received in communication unit 21 ofsecond information processor 40, and is transferred to port assigningpacket transmitter 41.

(Step S602) Port number differential detection packet transmitter 25 ofsecond information processor 40 transmits port number differentialdetection packet to server 50. In this transmission, ports of secondcommunication control unit 4 allowing to pass plural port numberdifferential detection packets are mutually different. The port numberdifferential detection packets are transmitted, for example, from pluralports of different port numbers in second information processor 40.

(Step S603) Port number differential information detector 93 of server50 receives the port number differential detection packets sent fromsecond information processor 40. Port number differential informationdetector 93 detects the position of ports of second communicationcontrol unit 4 allowing to pass the port number differential detectionpackets included in the header of port number differential detectionpackets.

(Step S604) Port number information transmitter for detecting portnumber 94 transmits the port differential information which is theinformation showing the position of ports of second communicationcontrol unit 4 allowing to pass the port number differential detectionpackets detected by port number differential information detector 93, tosecond information processor 40. The port differential information isreceived in port differential information receiver 84 in secondinformation processor 40.

(Step S605) Port number differential detector 85 detects the port numberdifferential of second information control unit 4 on the basis of theport differential information received in port differential informationreceiver 84. The port number differential is detected in the same manneras in preferred embodiment 1, and its explanation is omitted.

(Step S606) Range detection packet transmitter 23 transmits a rangedetection packet to server 50 by way of second communication controlunit 4. In this transmission, the packet is transmitted so that therange detection packet may pass through the latest assigned port insecond communication control unit 4. This is intended to properly limitthe range of ports including the bubble packet transmitting port. Forexample, range detection packet transmitter 23 transmits the rangedetection packet by using a port of second information processor 40 notused so far in communication.

(Step S607) Detector for detecting port number 91 of server 50 receivesthe range detection packet transmitted from second information processor40. Detector for detecting port number 91 detects the position of portof second communication control unit 4 allowing to pass this portdetection packet included in the header of the range detection packet.

(Step S608) Port number information transmitter for detecting portnumber 92 transmits the information for port differential detectionshowing the position of port of second communication control unit 4allowing to pass the range detection packet, detected by detector fordetecting port number 91, to second information processor 40. Thisinformation for port differential detection is received in portdifferential information receiver 81 in second information processor 40.

(Step S609) Port assigning packet transmitter 41 transmits a portassigning packet to first communication control unit 3. The address offirst communication control unit 3 is the one transmitted at step S601.

(Step S610) Range detection packet transmitter 23 transmits a rangedetection packet to server 50 by way of second communication controlunit 4.

(Step S611) Detector for detecting port number 91 of server 50 receivesthe range detection packet transmitted from second information processor40. Detector for detecting port number 91 detects the position of portof second communication control unit 4 allowing to pass this portdetection packet included in the header of the range detection packet.

(Step S612) Port number information transmitter for detecting portnumber 92 transmits the information for port differential detectionshowing the position of port of second communication control unit 4allowing to pass the range detection packet, detected by detector fordetecting port number 91, to second information processor 40. Thisinformation for port differential detection is received in portdifferential information receiver 81 in second information processor 40.

(Step S613) Range detector 82 of second information processor 40acquires the position of ports of second communication control unit 4allowing to pass range detection packets transmitted at steps S606,S610, from the information for port differential detection received inport differential information receiver 81, and on the basis of positionof two ports, the range of ports including the port assigning packettransmitting port (target port for transmitting bubble packet) isdetected. The target port for transmitting bubble packet may be eitherone port or may include two or more ports.

(Step S614) Port number differential information transmitter 86 ofsecond information processor 40 transmits the port number differentialinformation showing the port number differential of second communicationcontrol unit 4 detected at step S605, to server 50, together withinstruction for transmitting this port number differential informationto first information processor 30. Target port transmitter fortransmitting bubble packet 42 of second information processor 40transmits target port information for transmitting bubble packet showingthe target port for transmitting bubble packet detected at step S613, toserver 50, together with instruction for transmitting the target portinformation for transmitting bubble packet to first informationprocessor 30. These items of information may be transmitted by onepacket, or by different packets.

(Step S615) Communication unit 61 of server 50 receives port numberdifferential information and target port information for transmittingbubble packet, and sends these items of information to first informationprocessor 30. The target port for transmitting bubble packet is receivedin target port receiver for transmitting bubble packet 97, andtransmitted to first information processor 30 by target port transmitterfor transmitting bubble packet 65. The port number differentialinformation is received in port number differential receiver 18 of firstinformation processor 30, and target port information for transmittingbubble packet is received in target port receiver for transmittingbubble packet 16.

(Step S616) Information transmitter and receiver 62 of server 50transmits address information showing the IP address of secondcommunication control unit 4 to first information processor 30. Thetransmitted address information is received in communication unit 11 offirst information processor 30, and is transferred to bubble packettransmitter 12.

(Step S617) Packet transmitter for port differential detection 15 infirst information processor 30 transmits a port number differentialdetection packet to server 50. In this transmission, ports of firstcommunication control unit 3 allowing to pass plural port numberdifferential detection packets should be different from each other. Theport number differential detection packets are transmitted, for example,from plural ports different in port numbers of first informationprocessor 30.

(Step S618) Port number differential information detector 93 of server50 receives the port number differential detection packet transmittedfrom first information processor 30. Port number differentialinformation detector 93 detects the position of port of firstcommunication control unit 3 allowing to pass the port numberdifferential detection packet included in the header of the port numberdifferential detection packet.

(Step S619) Port number information transmitter for detecting portnumber 94 transmits the port number information for port differentialdetection showing the position of port of first communication controlunit 3 allowing to pass the port number differential detection packetdetected by port number differential information detector 93 to firstinformation processor 30. The port number information for portdifferential detection is received in port number differentialinformation receiver 74 in first information processor 30.

(Step S620) Port number differential detector 75 detects the port numberdifferential of first communication control unit 3 on the basis of theport number information for port differential detection received in portnumber differential information receiver 74. The port numberdifferential is detected in the same manner as in preferred embodiment1, and its explanation is omitted.

(Step S621) Range detection packet transmitter 13 transmits the rangedetection packet to server 50 by way of first communication control unit3.

(Step S622) Detector for detecting port number 91 of server 50 receivesthe range detection packet sent from first information processor 30.Detector for detecting port number 91 detects the position of port offirst communication control unit 3 allowing to pass this port detectionpacket.

(Step S623) Port number information transmitter for detecting portnumber 92 transmits the port number information for port differentialdetection showing the position of port of first communication controlunit 3 allowing to pass the range detection packet detected by detectorfor detecting port number 91 to first information processor 30. The portnumber information for port differential detection is received in portdifferential information receiver 71 in first information processor 30.

(Step S624) Bubble packet transmitter 12 transmits the IP address ofsecond communication control unit 4 indicated by the address informationtransmitted at step S616, and a bubble packet to the target port fortransmitting bubble packet of second communication control unit 4, onthe basis of target port information for transmitting bubble packettransmitted at steps S614 and S615. When the target port fortransmitting bubble packet includes two or more ports, the bubble packettransmitter 12 transmits bubble packets at every port numberdifferential indicated by the port differential information received inport number differential receiver 18.

(Step S625) Range detection packet transmitter 13 transmits a rangedetection packet to server 50 by way of first communication control unit3.

(Step S626) Detector for detecting port number 91 of server 50 receivesthe range detection packet sent from first information processor 30.Detector for detecting port number 91 detects the position of port offirst communication control unit 3 allowing to pass this port detectionpacket.

(Step S627) Port number information transmitter for detecting portnumber 92 transmits the port number information for port differentialdetection showing the position of port of first communication controlunit 3 allowing to pass the range detection packet detected by detectorfor detecting port number 91 to first information processor 30. The portnumber information for port differential detection is received in portdifferential information receiver 71 in first information processor 30.

(Step S628) Range detector 72 of first information processor 30 acquiresthe position of ports of first communication control unit 3 allowing topass range detection packets transmitted at steps S621, S622, from theinformation for port differential detection received in portdifferential information receiver 71, and on the basis of position oftwo ports, the range of ports including the port assigning packettransmitting port is detected. The range of port may be either one portor may include two or more ports.

(Step S629) Range transmitter 73 of first information processor 30transmits the range information showing the range of ports detected atstep S628 to server 50 together with instruction for transmitting therange information to second information processor 40. Port numberdifferential information transmitter 76 transmits the port numberdifferential information showing the port number differential of firstcommunication control unit 3 detected at step S620 to server 50 togetherwith an instruction for transmitting to the port number differentialinformation to second information processor 40. The range informationand port number differential information may be transmitted by onepacket, or by different packets.

(Step S630) Communication unit 61 of server 50 receives the rangeinformation and port number differential information, and sends therange information and other to second information processor 40. Therange information is received in range receiver 27 of second informationprocessor 40. The port number differential information is port numberdifferential receiver 28.

(Step S631) Reply packet transmitter 29 sends a reply packet to firstcommunication control unit 3 specified by the IP address showing theaddress information received at step S601. The reply packet istransmitted in every port number differential showing the port numberdifferential information, to the ports in the range indicated by therange information received from the range receiver 27.

(Step S632) Reply packet receiver 14 of first information processor 30receives the reply packet sent from second information processor 40. Byreceiving this reply packet, communication between first informationprocessor 30 and second information processor 40 is established.Afterwards, the information can be transmitted and received betweenfirst information processor 30 and second information processor 40without resort to server (for example, tunnel communication isestablished).

In FIG. 31 to FIG. 33, detection of port number differential may beanywhere before transmission of port number differential informationand, for example, the port number differential information may be sentto the reception side right after detection of port number differential.Or transmission of address of transmission side (step S601) may besimultaneous with transmission of port number information for portdifferential detection (step S608). Thus, in FIG. 31 to FIG. 33, thereis a certain freedom about sequence of process. In FIG. 32, transmissionof range detection packet and transmission of port assigning packet(steps S606, S609, S610), or transmission of range detection packet andtransmission of bubble packet (steps S621, S624, S625) may be executedwithout waiting for reception of port number information for portdifferential detection.

Operation of communication system of the preferred embodiment isexplained by referring to specific examples. In the specific examples,IP addresses of first communication unit 3 and others are same as inspecific examples in preferred embodiment 1, except that first server 6is replaced by server 50.

Second information processor 40 is supposed to be at sending/callingside. In the following specific examples, example 1 refers to a case inwhich second communication control unit 4 is other than PS NAT. Inexample 2, second communication control unit 4 is PS NAT, and firstcommunication control unit 3 is other than PS NAT.

In the specific examples, in order to transmit and receive packetsefficiently between server 50 and first information processor 30, orbetween server 50 and second information processor 40, determination oftransmission and reception (step S101) and establishment ofcommunication (step S102) are partly processed in parallel.

EXAMPLE 1

FIG. 34 to FIG. 38 explain this example. First information processor 30and second information processor 40 are accessing server 50, and it issupposed that the IP address of first communication control unit 3, theport number of port P1 of first communication control unit 3, and thedevice ID of first information processor 30 have been already held inserver 50. Similarly, the IP address of second communication controlunit 4, the port number of port P2 of second communication control unit4, and the device ID of second information processor 40 have beenalready held in server 50.

First, operation of requesting connection from second informationprocessor 40 is explained. In FIG. 34, second information processor 40transmits device ID of first information processor 30 and connectionrequest to server 50. As a result, server 50 transmits the IP address offirst communication control unit 3 and port number of port P1 to secondinformation processor 40 (step S601). This transmission is executedthrough port P2.

Packet transmitter for detecting port number 25 of second informationprocessor 40 transmits three port number differential detection packets(packets of UDP) from ports LP0, LP1, LP2 of second informationprocessor 40, respectively. Herein, ports LP0, LP1, LP2 are differentports newly assigned in second information processor 40. Therefore,regardless of the characteristic of second communication control unit 4,each port number differential detection packet is transmitted to server50 by way of different ports P5, P6, P7 in second communication controlunit 4 (step S602). Each port number differential detection packet isreceived in detector for detecting port number 93 by way ofcommunication unit 61 of server 50, and the port numbers of ports P5,P6, P7 of second communication control unit 4 included in the header ofeach packet are detected (step S603). Port number informationtransmitter for detecting port number 94 transmits the port differentialinformation which is the packet containing each port number in thepayload, to the ports of second communication control unit 4 allowing topass each port number differential detection packet (step S604). Morespecifically, to the port number differential detection packettransmitted through port P5, the port differential information includingthe port number of port P5 in its payload is transmitted by way of portP5. The port differential information is converted in address in secondcommunication control unit 4, and is transmitted to port LP0 of secondinformation processor 40. This port differential information is receivedin port differential information receiver 84 by way of communicationunit 21. Similarly, through ports P6, P7, the port differentialinformation is transmitted to second information processor 40. In thisexample, since the port number differential is detected by using alsothe range detection packet, the port number differential is not detectedat this stage. The port number differential detection packet transmittedthrough port P7 serves also characteristic determination packet as thepacket for determining the characteristic of second communicationcontrol unit 4, and therefore the port differential informationtransmitted through port P7 of second communication control unit 4 isalso transferred to characteristic determination unit 43 fromcommunication unit 21.

Range detection packet transmitter 23 of second information processor 40transmits the range detection packet (a packet of UDP) from port LP2 toport P3 of server 50 (step S606). In this specific example, this rangedetection packet serves also as port number differential detectionpacket.

Port P3 is a port different from port P4 as transmission destination ofport number differential detection packet. Therefore, when the portassigning rule of second communication control unit 4 is port sensitivetype, that is, when PS NAT is used in second communication control unit4, port P8 in second communication control unit 4 allowing to pass therange detection packet is a port different from port P7 allowing to passthe port number differential detection packet transmitted from port LP2,but when the port assigning rule of second communication control unit 4is other than port sensitive type, port P7 and port P8 are the sameport.

Detector for detecting port number 91 of server 50 receives the rangedetection packet transmitted to port P3 by way of communication unit 61.Detector for detecting port number 91 detects the port number of port P8of second communication control unit 4 included in the header of itspacket (step S607). Port number information transmitter for detectingport number 92 transmits the port differential information including theport number of detected port P8 in the payload to port P8 of secondcommunication control unit 4 (step S608). The port differentialinformation is converted in address in second communication control unit4, and transmitted to port LP2 of second information processor 40, andreceived in port differential information receiver 81. In this example,the range detection packet transmitted to port P3 of server 50 servesalso as port number differential detection packet and characteristicdetermination packet, and hence the port differential information isalso transferred from communication unit 21 to port differentialinformation receiver 84 and characteristic determination unit 43.

In this example, since the characteristic determination packet servesalso as port number differential detection packet and range detectionpacket, port detector for characteristic determination 95 and portdifferential information transmitter for characteristic determination 96of server 50 are not used.

Port number differential detector 85 detects the port numberdifferential of second communication control unit 4 on the basis of portnumbers of ports P5, P6, P7, P8 of second communication control unit 4received in port differential information receiver 84 (step S605). Morespecifically, if the difference of port P8 and port P7 is not zero, thesmallest value of difference between port P6 and port P5, differencebetween port P7 and port P6, and difference between port P8 and port P7is detected as the port number differential of second communicationcontrol unit 4. On the other hand, if the difference of port P8 and portP7 is zero, the smaller value of difference between port P6 and port P5and difference between port P7 and port P6 is detected as the portnumber differential of second communication control unit 4. In thisexample, since second communication control unit 4 is not PS NAT, thedifference of port P8 and port P7 is zero. In this example, it issupposed that the port number differential is detected to be 1.

Characteristic determination unit 43 determines the characteristic ofsecond communication control unit 4 on the basis of port numbers ofports P7 and P8 (step S501). More specifically, when port P7 and port P8are the same, the characteristic of second communication control unit 4is determined to be any one of full cone NAT, R NAT, PR NAT (these threeaddress assigning types are NAT of cone, which is called cone systemNAT), and AS NAT (that is, the port assigning rule is cone type oraddress sensitive type), and if port P7 and port P8 are different, thecharacteristic of second communication control unit 4 is determined tobe PS NAT type (that is, the port assigning rule is port sensitivetype). In this example, since second communication control unit 4 is notin PS NAT type, as mentioned above, port P7 and port P8 are the same,and characteristic determination unit 43 determines that secondcommunication control unit 4 is not in PS NAT (step S502). As a result,second information processor 40 at sending/calling side operates asinformation processor at reception side (step S503).

Port assigning packet transmitter 41 of second information processor 40,using the address of first communication control unit 3 transmitted fromserver 50, transmits the port assigning packet as packet of UDP to portP1 of first communication control unit 3 (step S609). This portassigning packet is also transmitted from port LP2 of second informationprocessor 40. This port assigning packet is transmitted through port P9of second communication control unit 4. When AS NAT is used in secondcommunication control unit 4, port P8 and port P9 are different, andwhen cone system NAT is used in second communication control unit 4,port P8 and port P9 are the same. By setting the life of the portassigning packet (for example, TTL set in this packet), it may bedesigned to extinguish before the port assigning packet reaches port P1.Port assigning packet is transmitted in order to leave transmissionrecord in second communication control unit 4, and it is notparticularly required that the port assigning packet may reach up tofirst communication control unit 3.

Range detection packet transmitter 23 transmits the range detectionpacket as packet of UDP from port LP3 of second information processor 40to port P4 of server 50 (step S610). Port LP3 is a port newly assignedin second information processor 40, different from any of ports LP0,LP1, LP2. The range detection packet is transmitted by way of port P10of second communication control unit 4. Herein, port P10 is differentfrom any one of ports P7, P8, P9. The range detection packet is receivedin detector for detecting port number 91 of server 50, and the portnumber of port P10 included in the header is detected (step S611). Theport differential information including this port number is transmittedfrom port number information transmitter for detecting port number 92 tosecond information processor 40 by way of port P10 (step S612). Thisport differential information is received in port differentialinformation receiver 81 of second information processor 40. The range oftarget port for transmitting bubble packet is detected by range detector82 (step S613). In this detection, the range from the port position ofport P8 to the port position to be assigned one port before port P10 isdetected as target ports for transmitting bubble packet. Depending onthe characteristic of second communication control unit 4, port P8 andport P9 may be the same, but regardless of the characteristic of secondcommunication control unit 4, port P9 and port P10 are always different.The port position to be assigned one port before port P10 is the portposition indicated by the port number by subtracting the port numberdifferential (1 in this example) of second communication control unit 4detected by port number differential detector 85, from the port numberof port P10. Target port transmitter for transmitting bubble packet 42transmits the target port information for transmitting bubble packetindicating the target port for transmitting bubble packet detected byrange detector 82, to server 50, together with instruction fortransmission to first information processor 30 (step S614). Port numberdifferential information transmitter 86 transmits the port numberdifferential information showing the port number differential of secondcommunication control unit 4, to server 50, together with instructionfor transmission to first information processor 30 (step S614).Characteristic transmitter 44 transmits the information showing thecharacteristic of second communication control unit 4, that is, thecharacteristic information showing PS NAT is not used in secondcommunication control unit 4, to server 50, together with instructionfor transmission to first information processor 30.

These items of information are relayed by server 50, and transmitted tofirst information processor 30 by way of port P1 of first communicationcontrol unit 3 (step S615). The target port information for transmittingbubble packet is received in target port receiver for transmittingbubble packet 16. The port number differential information is receivedin port number differential receiver 18, and is transferred to bubblepacket transmitter 12 by way of a route not shown. Characteristicinformation is transferred to packet transmitter for port differentialdetection 15, range detection packet transmitter 13, bubble packettransmitter 12, and others, and since PS NAT is not used in secondcommunication control unit 4, first information processor 30 is judgedto be responsible for processing sequence as the transmission sidedevice.

Server 50 transmits the IP address of reception side secondcommunication control unit 4 to first information processor 30 (stepS616).

Packet transmitter for port differential detection 15 of firstinformation processor 30 transmits the port number differentialdetection packets which are UDP packets, from different ports LP4, LP5of first information processor 30 to port P3 of server 50 (step S617).These port number differential detection packets are transmitted toserver 50 by way of different ports P11, P12 of first communicationcontrol unit 3, and are received in port number differential informationdetector 93. In port number differential information detector 93, portnumbers of ports P11, P12 are detected same as in the case of portnumber differential detection packet transmitted from second informationprocessor 40 (step S618). Port number information transmitter fordetecting port number 94 transmits the port differential informationwhich is the packet including the detected port numbers of ports P11,P12 in the payload, to first information processor 30 by way of portsP11, P12, respectively (step S619). The port differential information isreceived in port number differential information receiver 74. In thisexample, the port number differential is detected also by using therange detection packet, the port number differential is not detected asthis stage.

Range detection packet transmitter 13 transmits the range detectionpacket as UDP packet from port LP6 of first information processor 30(step S621). This range detection packet is transmitted to port P3 ofserver 50 by way of port P13 of first communication control unit 3.Herein, the range detection packet serves also as port numberdifferential detection packet. Port LP6 is a port newly assigned infirst information processor 30, different from ports LP4, LP5.

The range detection packet is received in detector for detecting portnumber 91 of server 50, and port number of port P13 is detected (stepS622). Port number information transmitter for detecting port number 92transmits the port differential information which is a packet includingthe detected port number of port P13 in the payload, to firstinformation processor 30 by way of port P13 (step S623). The portdifferential information is received in port differential informationreceiver 71, and this range detection packet serves also as port numberdifferential detection packet, and hence communication unit 11 transfersthis port differential information also to port number differentialinformation receiver 74.

Port number differential detector 75 detects the port numberdifferential of first communication control unit 3, on the basis of portnumbers of ports P11, P12, P13 of first communication control unit 3received in port differential information receiver 84 (step S620). Morespecifically, the smaller value of difference of port P12 and port P11and difference of port P13 and port P12 is detected as the portdifferential number of first communication control unit 3. In thisexample, port number differential of 1 is detected.

Bubble packet transmitter 12 transmits bubble packets to target portsfor transmitting bubble packet in a range indicated by target portinformation for transmitting bubble packets (step S624). The bubblepacket is transmitted from port LP6 of first information processor 30.If the range of target port for transmitting bubble packet includesplural ports, the bubble packets are transmitted in every port numberdifferential (in every 1 in this example) indicated by the portdifferential information of second communication control unit 4 receivedin port number differential receiver 18. In this example, as shown inFIG. 37, suppose the bubble packets are transmitted by way of ports fromport P14 to port P15 of first communication control unit 3. Depending onthe characteristic of the second communication control unit 4, thebubble packet may be received in port LP2, but in this example, theprocess is further continued in order to establish the communicationsecurely between first information processor 30 and second informationprocessor 40.

Range detection packet transmitter 13 transmits the range detectionpacket from port LP7 of first information processor 30 to port P3 ofserver 50 (step S625). Port LP7 and port LP6 are different ports, andare ports newly assigned in first information processor 30. Since portLP7 is a new port, port P16 allowing to pass the range detection packetis a port different from port P15. The range detection packettransmitted through port P16 is received in detector for detecting portnumber 91 of server 50, and the port number of port P16 is detected(step S626). Port number information transmitter for detecting portnumber 92 transmits the port differential information which is a packetincluding the detected port number in payload to first informationprocessor 30 by way of port P16 of first communication control unit 3(step S627). The port differential information transmitted from server50 is received in port differential information receiver 71. Rangedetector 72 detects the range of ports including the bubble packettransmitting port on the basis of port positions of port P13 and portP16 (step S628). In this detection, the range from the port position ofport P13 to the port position to be assigned one port before port P16 isdetected as range including the port for transmitting bubble packet.Regardless of the characteristic of first communication control unit 3,port P15 and port P16 are always different, and port P16 is not includedin this range. The port position to be assigned one port before port P16is the port position indicated by the port number by subtracting theport number differential (1 in this example) of first communicationcontrol unit 3 detected by port number differential detector 75, fromthe port number of port P16. Range transmitter 73 transmits the rangeinformation showing the range of ports detected by range detector 72, toserver 50, together with instruction for transmission to secondinformation processor 40 (step S629). Port number differentialinformation transmitter 76 transmits the port number differentialinformation showing the port number differential of first communicationcontrol unit 3, to server 50, together with instruction for transmissionto second information processor 40 (step S629).

These items of information are relayed by server 50, and transmitted tosecond information processor 40 by way of port P2 of secondcommunication control unit 4 (step S630). The range information isreceived in range receiver 27. The port number differential informationis received in port number differential receiver 28. Reply packettransmitter 29 sends reply packet to the port in the range indicated bythe range information received in the range receiver 27 (step S631).

The reply packet is sent from port LP6 of first information processor30. If the range information is a range including plural ports, thereply packet is transmitted in every port number differential (1 in thisexample) indicated by the port number differential information of firstcommunication control unit 3 received in the port number differentialreceiver 28. In this example, as shown in FIG. 38, the reply packet istransmitted by way of port P9 of second communication control unit 4.Since PS NAT is not used in second communication control unit 4, allreply packets to be transmitted to first communication control unit 3have been already-sent by way of port P9. Thus, in order that all replypackets be transmitted from port P9, second information processor 40 hasprimarily sent all port assigning packets to first communication controlunit 3 from port LP2.

Of the reply packets sent from second information processor 40, thereply packet sent to the bubble packet transmitting port allowing topass the bubble packet sent to port P9 is converted in address in firstcommunication control unit 3, and is received in reply packet receiver24 of first information processor 30 (step S632). Depending on thecharacteristic of first communication control unit 3, plural replypackets may be received in first information processor 30.

Thus, communication between first information processor 30 and secondinformation processor 40 is established.

In the communication system of the preferred embodiment, the reason oftransmitting the port assigning packet is briefly explained. Beforetransmission of bubble packet, by transmitting the port assigning packetto the first communication control unit 3, port P9 is assigned in secondcommunication control unit 4. Since PS NAT is not used in the receptionside device (see FIG. 29), PS NAT is not used in second communicationcontrol unit 4 (that is, the port assigning rule is not port sensitivetype). Therefore, from port LP2 transmitting this port assigning packet,by transmitting the reply packet to first communication control unit 3,the reply packet is transmitted through port P9 of second communicationcontrol unit 4 assigned by transmission of port assigning packet.

By detecting the range including this port P9, and transmitting thebubble packet to this range, at least one bubble packet can betransmitted to port P9. Then, in the range of ports including the bubblepacket transmitting port, by sending the reply packet from port LP2, thereply packet can be sent to the port of first communication control unit3 allowing to pass the bubble packet transmitted to port P9, by way ofport P9. As a result, if PR NAT or PS NAT is used in first communicationcontrol unit 3, the reply packet is received in first informationprocessor 30, and communication between first information processor 30and second information processor 40 is established. Thus, the portassigning packet is transmitted in order to assign the passing port ofreply packet preliminarily in second communication control unit 4 (inother words, to determine the range of target ports for transmittingbubble packet).

EXAMPLE 2

In example 2, PS NAT is used in second communication control unit 4, andother than PS NAT is used in first communication control unit 3. Same asin example 1, second information processor 40 is at sending/callingside.

Second information processor 40 transmits port number differentialdetection packet, range detection packet, and port assigning packet, andthe port number differential of second communication control unit 4 isdetected, the position of target port for transmitting bubble packet isdetected, and the characteristic of second communication control unit 4is determined, and this series of operation is same as in example 1.

As the port number differential information, target port information fortransmitting bubble packet, and characteristic are transmitted fromsecond information processor 40 by way of server 50 (steps S614, S615),first information processor 30 knows that PS NAT is used in secondcommunication control unit 4. As a result, first information processor30 executes the process from step S601 to step S614, and the judgingprocess (process explained in FIG. 34 and FIG. 35 in example 1) todetermine the characteristic of first communication control unit 3 ofreceiving side (first information processor 30 side) at step S504. Theseprocesses are same as in example 1, except that the reception side andtransmission side are exchanged, and its explanation is omitted. In thisexample, since PA NAT is not used in first communication control unit 3,the receiving side is judged to be reception side (step S506). In thestate of exchange of reception side and transmission side in example 1,transmission of bubble packet, detection of range including bubblepacket transmitting port, and transmission of reply packet areconducted, and communication is established between first informationprocessor 30 and second information processor 40. This is same as inexample 1, and explanation is omitted.

In the foregoing examples, the port assigning packet is explained to betransmitted from the same port (port LP2) as the port used fortransmitting the first range detection packet, but the port assigningpacket may be transmitted from the same port (port LP3) as the port usedfor transmitting the second range detection packet. In this case, thetarget ports for transmitting bubble packet range from the port assignednext to port P8 to port P10. Otherwise the port assigning packets andtwo range detection packets may be transmitted from different ports(ports newly assigned in second information processor 40, respectively).In this case, the target ports for transmitting bubble packet range fromthe port assigned next to the port of second communication control unit4 allowing to pass the first range detection packet to the port assignedone port before the port of second communication control unit 4 allowingto pass the second range detection packet. These target ports fortransmitting bubble packet are explained as a minimum range of ports,and target ports for transmitting bubble packet may be specified in awider range than the range including these target ports for transmittingbubble packet.

Similarly, the bubble packet may be transmitted from port LP7, insteadof port LP6. In this case, too, the reply packet transmitting range isfrom the port assigned next to port P13 to port P16. Or the bubblepacket and second range detection packet may be transmitted fromdifferent ports (ports newly assigned in first information processor 30,respectively). In this case, the range of ports including the bubblepacket transmitting port ranges from the port assigned next to the portof first communication control unit 3 allowing to pass the first rangedetection packet, to the port assigned one port before the port of firstcommunication control unit 3 allowing to pass the second range detectionpacket. The range of these ports-including the ports for transmittingbubble packet are explained as a minimum range of ports, and a widerrange than the range including these may be defined as a range of portsincluding ports for transmitting bubble packet.

In the specific examples, in order to decrease the number of times ofcommunication between server 50 and information processor, one packethas plural roles, and efficient communication of packet is explained,but the packet may be also transmitted so that one packet may have onerole only. In the examples, characteristic determination ofcommunication control unit, and establishment of communication betweeninformation processors are executed in parallel, but these processes maybe done separately. In such a case, in determination of characteristic,characteristic determination port detector 95 and characteristicdetermination port information transmitter 96 may be used.

Thus, according to the communication system of the preferred embodiment,except when PS NAT is used in both first communication control unit 3and second communication control unit 4, communication is establishedbetween first information processor 30 and second information processor40. Further, only by checking if PS NAT is used in the communicationcontrol unit or not, the establishment of communication can be executedwithout requiring further particular determination.

In the method of preferred embodiment 1, when PR NAT is used intransmission side device, it is required to exchange transmission andreception (see FIG. 17), but in the method of this preferred embodiment,it is not required to exchange transmission and reception even if RP NATis used in either transmission side or reception side informationprocessor. Therefore, when the cone system NAT is used in thecommunication system, communication between information processors canbe established without exchanging transmission and reception (see FIG.39).

In the preferred embodiment, since it is not required to determinewhether AS NAT is used or not in the communication control unit (it isonly required to determine whether PS NAT is used or not), it is notnecessary to specify the communication control unit using two or moreservers, and a simple configuration of communication system is realized.

In the preferred embodiment, it is explained that detection of portnumber differential, detection of range of ports including bubble packettransmitting port, and detection of target port for transmitting bubblepacket are executed in the information processor, one or more arbitraryprocesses of these processes may be executed in server 50 same as inpreferred embodiment 1.

In the preferred embodiment, in order to detect the target port fortransmitting bubble packet, two range detection packets are transmittedbefore and after transmission of port assigning packet, but bytransmitting only one range detection packet, the target portinformation for transmitting bubble packet may show only the upper limitor lower limit of the target port for transmitting bubble packet. Inthis case, bubble packets may be transmitted to all ports included inthe range.

Or, the bubble packet may be transmitted to all ports in the receptionside communication control unit. In this manner, bubble packets can betransmitted to all ports used in transmission of port assigning packet.Herein, in spite of all ports, well-known ports of which application isalready known may be excluded, and the reply packet may be transmittedto other than well-known ports. When transmitting the bubble packet toevery specified port number differential, the position of the port asthe base point maybe noticed to the transmission side informationprocessor.

In the preferred embodiment, too, even in the communication system nothaving one communication control unit, communication between informationprocessors can be established same as in preferred embodiment 3.

In the foregoing preferred embodiments, the communication system is acommunication system comprising information processors for transmittingbubble packets, and a server (or two or more servers) for processingdetection of range of ports including bubble packet transmitting port,and it may be designed to detect the range of ports including the bubblepacket transmitting port. That is, the communication system of theinvention may be a communication system as described below. Thecommunication system is a communication system comprising an informationprocessor, a communication control unit for controlling thecommunication of the information processor, and a server, in which theinformation processor includes a bubble packet transmitter fortransmitting one or more bubble packets for leaving transmission recordin the communication control unit, and a range detection packettransmitter for transmitting the range detection packet used fordetecting the range of ports including one or more bubble packettransmitting ports as ports of the communication control unit used intransmission of one or more bubble packets, to the server, and theserver includes a range detector for detecting the range of portsincluding the one or more bubble packet transmitting ports on the basisof the range detection packet by receiving the range detection packet.In this communication system, the transmission destination of bubblepacket may be, for example, other communication control unit as thecommunication partner of the information processor, or the communicationcontrol unit for controlling communication of other informationprocessor as communication partner. In the communication system, therange of ports detected by the server may be transmitted to theinformation processor by transmitter, or transferred to the informationprocessor by other method. Other method includes, for example, a methodof recording the information showing the range of ports in a recordingmedium, and reading out the information from the recording medium by theinformation processor, or a method of displaying the information showingthe range of ports in the server, and allowing the user to see thedisplay and enter the information showing the range of ports in theinformation processor. Or, as shown in preferred embodiment 4, one ormore bubble packets may be transmitted in the communication system.

Other communication system is a communication system comprising aninformation processor, a communication control unit for controlling thecommunication of the information processor, and a server, in which theinformation processor includes a bubble packet transmitter fortransmitting one or more bubble packets for leaving transmission recordin the communication control unit, a range detection packet transmitterfor transmitting the range detection packet used for detecting the rangeof ports including one or more bubble packet transmitting ports as portsof the communication control unit used in transmission of one or morebubble packets, to the server, a port differential information receiverfor receiving the port differential information showing the position ofthe port of communication control unit allowing to pass the rangedetection packet, and a range detector for detecting the range of portsincluding one or more bubble packet transmitting ports on the basis ofthe port differential information received in the port differentialinformation receiver, and the server includes a detector for detectingport number by receiving the range detection packet and detecting theposition of the port of the communication control unit allowing to passthe range detection packet, and a port number information transmitterfor detecting port number for transmitting the port differentialinformation showing the position of the port detected by the detectorfor detecting port number to the information processor. In this manner,the range may be detected by the information processor, instead of theserver. In this communication system, the transmission destination ofbubble packet may be, for example, other communication control unit asthe communication partner of the information processor, or thecommunication control unit for controlling communication of otherinformation processor as communication partner. In the communicationsystem, the range of ports detected by the information processor may betransmitted to other information processor by transmitter, ortransferred to the other information processor by other method. Othermethod includes, for example, a method of recording the informationshowing the range of ports in a recording medium, and reading out theinformation from the recording medium by the information processor, or amethod of displaying the information showing the range of ports in theinformation processor, and allowing the user to see the display andenter the information showing the range of ports in the informationprocessor. Or, as shown in preferred embodiment 4, one or more bubblepackets may be transmitted in the communication system.

In the foregoing embodiments, first servers 6, 60 and server 50 functionto notice IP address of partner side communication control unit to theinformation processor, but this function may be realized by other serverthan first server 6, etc. That is, the server for noticing the addressof other communication control unit to one information processor may bedifferent from the server for processing about range detection packet,etc. On the other hand, in process about notice of address of othercommunication control unit to one information processor, or in processabout calling of partner side (receiving side) information process bysending/calling side information processor, SIP (session initiationprotocol) may be used.

In the explanation of the foregoing preferred embodiments, the replypacket is transmitted in every port number differential indicated by theport differential information, but the reply packet may be transmittedat port interval of 1 regardless of the port number differential.

In the explanation of the foregoing preferred embodiments, the replypacket is transmitted in a range of ports indicated by the rangeinformation, but the reply packet may be transmitted to all ports in thetransmission side communication control unit. In this manner, the replypacket can be transmitted to the bubble packet transmitting port used intransmission of bubble packet. By the range information, when the upperlimit or lower limit of the range is shown, the reply packet may betransmitted to all ports in this range. Herein, in spite of all ports,well-known ports of which application is already known may be excluded,and the reply packet may be transmitted to other than well-known ports.When transmitting the reply packet to every specified port numberdifferential, the position of the port as the base point may be noticedto the reception side information processor.

In the explanation of the foregoing preferred embodiments, too, the typeof NAT used in the communication control unit is determined in firstserver 6, etc. or information processor, but, for example, thecharacteristic (type of NAT) of communication control unit entered fromthe information processor by manual input or the like by the user may beheld in first server 6, etc., or may be stored in memory means (forexample, nonvolatile memory) held by communication control unit, and thecharacteristic of the communication control unit may be determined byreading the stores characteristic by first server 6, etc. Thecharacteristic of the communication control unit may be stored somewhereother than the communication control unit. For example, the databaseserver may store the characteristic by corresponding to the ID or typenumber of the communication control unit.

In the preferred embodiments, in first server 6, etc. or informationprocessor, the characteristic of the communication control unit isdetected, but the detection timing is not specified. That is, it may beafter request for establishment of communication from either informationprocessor, or the characteristic may be determined in advance when theinformation processor is connected to first server 6, etc.

The IP address of the communication control unit or the port numberdifferential of communication control unit may be transferred to theinformation processor by manual input by the user, instead of beingtransmitted from first server 6, etc., or the port number differentialstored in the communication control unit may be acquired.

As explained herein, the target port for transmitting bubble packet isnoticed from first server 6, etc. or reception side informationprocessor, to transmission side information processor, but the targetport for transmitting bubble packet may be preliminarily set in thetransmission side information processor, or the position of the targetport for transmitting bubble packet may be detected by transmission sideinformation processor by manual input by the user or access to specifiedserver.

In preferred embodiments 1 to 3, the first server and second servercommunicate directly with each other, but the first server and secondserver may share the information between servers (for example, portnumber of port P8 in FIG. 12), by way of specified shared recordingmedium.

In these preferred embodiments, in order to limit the target ports fortransmitting bubble packet to specified ports, it is mainly explained totransmit the target port information for transmitting bubble packet, butthe target port information for transmitting bubble packet is notintended to limit the target port for transmitting bubble packet, butmay be transmitted only for the purpose of specifying the port oftransmission destination of bubble packet.

In the preferred embodiments, each information processor is connected tocommunication network 5 through only one communication control unit, butif connected to communication network 5 through plural communicationcontrol units (that is, in the case of multi-stage connection NAT),communication between information processors can be established.

In the preferred embodiments, first communication control unit 3 andsecond communication control unit 4 have the NAT function, but firstcommunication control unit 3 and second communication control unit 4 mayhave, instead of the NAT function, or together with the NAT function,firewall function of packet filtering. The packet filtering is to selectthe reception packet on the basis of, for example, the reception filterrule. When first communication control unit 3 has the firewall functionon the basis of such reception filter rule, by leaving the transmissionrecord in first communication control unit 3 by transmission of bubblepacket from the local side (first information processor 1, etc. side) tothe global side (communication network 5), the reply packet transmittedto bubble packet transmitting port may be received. Or when secondcommunication control unit 4 has the fire wall function on the basis ofsuch reception filter rule, by transmission of reply packet from thelocal side (second information processor 2, etc. side) to the globalside by way of the target port for transmitting bubble packet,communication is established between first information processor 1, etc.and second information processor 2, etc.

Herein, first information processor 1, etc. and second informationprocessor 2, etc. may or may not support the firewall function asapplication.

In the preferred embodiments, first server 6 or the like is specified bythe IP address, but first server 6 or the like may be specified bydomain name (for example, server.pana.net or the like). In this case,the domain name is converted into IP address by using the DNS server,and first server 6 or the like can be specified.

The protocol used in communication in the preferred embodiments may beeither IPv4 (Internet protocol version 4) or IPv6 (Internet protocolversion 6).

In the preferred embodiments, each process (each function) may berealized by concentrated processing by a single device (system), orrealized by discrete processing by plural devices.

In the preferred embodiments, the constituent elements may be composedof exclusive hardware, or constituent elements that can be realized bythe software may be realized by the software by program control. Thesoftware for realizing the information processor in the preferredembodiments may include the following program. That is, the program is aprogram for executing the process in the first information processor forcommunicating with the second information processor, by way of the firstcommunication control unit for controlling the communication of thefirst information processor and the second communication control unitfor controlling the communication of the second information processor,and is intended to execute a bubble packet transmitting step oftransmitting the bubble packet for leaving the transmission record inthe first communication control unit to the second communication controlunit by way of the first communication control unit, and a reply packettransmitting step of receiving the reply packet transmitted to thebubble packet transmitting port as the port of the first communicationcontrol unit from the second information processor by way of the secondcommunication control unit.

In this program, the computer may further execute a range detectionpacket transmitting step of transmitting the range detection packet usedin detection of range of ports including the bubble packet transmittingport.

In this program, at the range detection packet transmitting step, therange detection packet may be transmitted before and after transmissionof bubble packet in the bubble packet transmitting step.

In this program, at the range detection packet transmitting step, therange detection packet may be transmitted before and after transmissionof bubble packet to mutually different addresses.

In this program, the computer may further execute a step of receivingthe target port for transmitting bubble packet for receiving the targetport information for transmitting bubble packet showing the position ofthe target port for transmitting bubble packet which is the target portfor transmitting the bubble packet in the second communication controlunit, and at the bubble packet transmitting step, the bubble packet maybe transmitted to the target port for transmitting bubble packetindicated by the target port information for transmitting bubble packet.

In this program, the target port for transmitting bubble packet may be aport for transmitting and receiving the information with the server forestablishing communication between the first information processor andsecond information processor by the second information processor.

In this program, the computer may further execute a port numberdifferential detection packet transmitting step of transmitting a portnumber differential detection packet for detecting the port numberdifferential in the first communication control unit by way of the firstcommunication control unit.

In this program, the first communication control unit transmits thebubble packet for leaving the transmission record in the secondcommunication control unit from the second information processor by wayof the second communication control unit, and the computer may alsoexecute a reply packet transmitting step of transmitting the replypacket to one or more ports at least including the port of the secondcommunication control unit used in transmission of the bubble packetfrom the second information processor.

In this program, the computer may further execute a range receiving stepof receiving the range information as the information showing the rangeof ports for transmitting the reply packet, and the reply packet may besent to the ports in the range indicated by the range information at thereply packet transmitting step.

In the program, the computer may further execute a port numberdifferential receiving step of receiving the port number differentialinformation as the information showing the port number differential inthe second communication control unit, and the reply packet may be sentin every port number differential indicated by the port numberdifferential information at the reply packet transmitting step.

The software for realizing the information processor in the preferredembodiments is the following program. That is, the program is a programfor executing the process in the first information processor forcommunicating with the second information processor, by way of the firstcommunication control unit for controlling the communication of thefirst information processor and the second communication control unitfor controlling the communication of the second information processor,in which the first communication control unit receives the bubble packetfor leaving the transmission record in the second communication controlunit, from the second information processor by way of the secondcommunication control unit, and executes the reply packet transmittingstep of sending the reply packet to one or more ports including at leastthe port of the second communication control unit used in transmissionof the bubble packet from the second information processor.

In this program, the computer may further execute a range receiving stepof receiving the range information as the information showing the rangeof ports for transmitting the reply packet, and the reply packet may besent to the ports in the range indicated by the range information at thereply packet transmitting step.

In the program, the computer may also execute a port number differentialreceiving step of receiving the port number differential information asthe information showing the port number differential in the secondcommunication control unit, and the reply packet may be sent in everyport number differential indicated by the port number differentialinformation at the reply packet transmitting step.

The software for realizing the server in the preferred embodiments isthe following program. That is, the program is a program for executingthe process in the server for establishing communication between thefirst information processor and second information processor, by way ofthe first communication control unit for controlling the communicationof the first information processor and the second communication controlunit for controlling the communication of the second informationprocessor, and is intended to execute an information transmitting andreceiving step of transmitting and receiving information between thefirst information processor and second information processor, acharacteristic determining step of determining the characteristic of thefirst communication control unit and second communication control unit,and a transmission and reception determining step of determining eitherone of the first information processor and second information processorat transmission side (transmission side information processor) and otherat reception side (reception side information processor) depending onthe judging result at the characteristic determining step.

In this program, the computer may further execute a transmitting step oftarget port for transmitting bubble packet for transmitting the targetport information for transmitting bubble packet indicating the positionof the target port for transmitting bubble packet as the target port fortransmitting the bubble packet for leaving the transmission record inthe communication control unit (transmission side communication controlunit) for controlling the communication of the transmission sideinformation processor by the transmission side information processor, tothe transmission side information processor.

In this program, the target port for transmitting bubble packetindicated by the target port information for transmitting bubble packetmay be the port of the reception side communication control unit, usedin communication between the information transmitter and receiver andthe reception side information processor.

In this program, the computer, receiving the range detection packet,from the transmission side information processor, for detecting therange of ports including the bubble packet transmitting port to thetarget port for transmitting bubble packet in the reception sidecommunication control unit, may further execute a range detecting stepof detecting the range of ports including the bubble packet transmittingport, and a range transmitting step of transmitting the rangeinformation as the information showing the range of ports including thebubble packet transmitting port detected at the range detecting step.

In this program, at the range detecting step, the range may be detectedon the basis of the range detection packet transmitted to pluraladdresses.

In this program, the computer, receiving the port number differentialdetection packet for detecting the port number differential in thetransmission side communication control unit transmitted from thetransmission side information processor by way of the transmission sidecommunication control unit, may further execute a port numberdifferential detecting step of detecting the port number differential inthe transmission side communication control unit on the basis of theport number differential detection packet, and a port numberdifferential transmitting step of transmitting the port numberdifferential information as the information showing the port numberdifferential of the transmission side communication control unitdetected at the port number differential detecting step.

In this program, the computer may further execute a detection portinformation receiving step of receiving the detection port informationshowing the position of the port of the first communication control unitallowing to pass the range detection packet, a range detecting step ofdetecting the range of ports including the bubble packet transmittingport on the basis of the detection port information received at thedetection port information receiving step, and a range transmitting stepof transmitting the range information as the information showing therange of ports including the bubble packet transmitting port detected atthe range detecting step.

In this program, the computer may further execute a port differentialinformation receiving step of receiving the port differentialinformation showing the position of the port in the first communicationcontrol unit allowing to pass the port number differential detectionpacket, a port number differential detecting step of detecting the portnumber differential in the first communication control unit on the basisof the port differential information received at the port differentialinformation receiving step, and a port number differential transmittingstep of transmitting the port number differential information as theinformation showing the port number differential of the firstcommunication control unit detected at the port number differentialdetecting step to the second information processor.

In this program, the computer may further execute a receiving step oftarget port for transmitting bubble packet of receiving the target portinformation for transmitting bubble packet indicating the position ofthe target port for transmitting bubble packet as the target port fortransmitting the bubble packet in the second communication control unit,and the bubble packet may be transmitted to the target port fortransmitting bubble packet indicated by the target port information fortransmitting bubble packet at the bubble packet transmitting packet.

In this program, the target port information for transmitting bubblepacket is the information showing the position of one or more targetports for transmitting the bubble packets, and at the bubble packettransmitting step, the bubble packet may be transmitted to one or moretarget ports for, transmitting bubble packet indicated by the targetport information for transmitting bubble packet.

In this program, the computer may further execute a port assigningpacket transmitting step of transmitting a port assigning packet forassigning the port for transmitting the reply packet in the firstcommunication control unit, and the reply packet may be transmitted fromthe port of the first information processor receiving the port assigningpacket at the reply packet transmitting packet.

In this program, the computer may further execute a range detectionpacket transmitting step of transmitting the range detection packet usedin detection of range of ports including the port assigning packettransmitting port as the port in the first communication control used intransmission of the port assigning packet.

The software for realizing the information processor in the preferredembodiments is the following program. That is, the program is a programfor causing the computer to execute the process in the informationprocessor for composing a communication system comprising an informationprocessor, a communication control unit for controlling thecommunication of the information processor, and a server, and isintended to execute a bubble packet transmitting step of transmittingone or more bubble packets for leaving the transmission record in thecommunication control unit by way of the communication control unit, anda range detection packet transmitting step of transmitting the rangedetection packet used in detection of range of ports including one ormore bubble packet transmitting ports as the ports of the communicationcontrol unit used in transmission of one or more bubble packets.

In this program, the computer may further execute a detection portinformation receiving step of receiving the detection port informationshowing the position of the port of the communication control unitallowing to pass the range detection packet, and a range detecting stepof detecting the range of ports including one or more bubble packettransmitting ports on the basis of the detection port informationreceived at the detection port information receiving step.

In this program, the computer may further execute a range transmittingstep of transmitting the range information as the information showingthe range of ports including one or more bubble packet transmittingports detected at the range detecting step.

The software for realizing the server in the preferred embodiments isthe following program. That is, the program is a program for causing thecomputer to execute the process in the server for composing acommunication system comprising an information processor, acommunication control unit for controlling the communication of theinformation processor, and a server, and is intended to execute, byreceiving the range detection packet transmitted from the informationprocessor used for detecting the range of ports including one or morebubble packet transmitting ports as ports of the communication controlunit used in transmission of one or more bubble packets transmitted forleaving the transmission record in the communication control unit, arange detecting step of detecting the range of ports including one ormore bubble packet transmitting ports on the basis of the rangedetection packet, and a range transmitting step of transmitting therange information as the information showing the range of portsincluding one or more bubble packet transmitting ports detected at therange detecting step.

Other program is a program for causing the computer to execute theprocess in the server for composing a communication system comprising aninformation processor, a communication control unit for controlling thecommunication of the information processor, and a server, and isintended to execute, by receiving the range detection packet transmittedfrom the information processor used for detecting the range of portsincluding one or more bubble packet transmitting ports as ports of thecommunication control unit used in transmission of one or more bubblepackets transmitted for leaving the transmission record in thecommunication control unit, a detection port detecting step of detectingthe position of the port of communication control unit allowing to passthe range detection packet, and a detection port informationtransmitting step of transmitting the detection port information showingthe position of the port detected at the detection port detecting stepto the information processor.

In these programs, in the transmitting step of transmitting informationor in the receiving step of receiving information, the process executedin the hardware, such as the process conducted in the modem or interfacecard at the transmitting step (the process executed only in thehardware) is not included.

The program may be distributed by downloading from the server or thelike, or may be distributed by recording from a specified recordingmedium (for example, optical disk such as CD-ROM or magnetic disk,semiconductor memory, etc.).

The computer for executing the program may be either one or plural. Thatis, either concentrated process or discrete process may be applied.

INDUSTRIAL APPLICABILITY

As described herein, in the communication system and others by theinvention, communication can be established between plural informationprocessors by way of a communication control unit, and it is very usefulfor communication between information processors.

1. A communication system comprising: a first information processor; asecond information processor; a first communication control unit forcontrolling the communication of the first information processor; aserver; and a second communication control unit for controlling thecommunication of the second information processor, wherein the firstinformation processor includes: a bubble packet transmitter fortransmitting a bubble packet for leaving transmission record in thefirst communication control unit to the second communication controlunit via the first communication control unit; a reply packet receiverfor receiving a reply packet transmitted from the second informationprocessor via the second communication control unit to a bubble packettransmitting port, a port of the first communication control unit, whichis used in transmission of the bubble packet; a range detection packettransmitter for transmitting a range detection packet used for detectinga range of ports including the bubble packet transmitting port to theserver, and a port number differential detection packet transmitter fortransmitting a port number differential detection packet for detecting aport number differential in the first communication control unit to theserver via the first communication control unit, the server includes: arange detector which receives the range detection packet for detectingthe range of ports including the bubble packet transmitting port inaccordance with the range detection packet; a range transmitter fortransmitting range information detected by the range detector asinformation showing the range of ports including the bubble packettransmitting port to the second information processor, a port numberdifferential detector which receives the port number differentialdetection packet for detecting a port number differential in the firstcommunication control unit in accordance with the port numberdifferential detection packet; and a port number differentialinformation transmitter for transmitting port number differentialinformation detected by the port number differential detector asinformation showing the port number differential of the firstcommunication control unit to the second information processor, thesecond information processor includes: a reply packet transmitter fortransmitting the reply packet to one or more ports including at leastthe bubble packet transmitting port; a range receiver for receiving therange information; and a port number differential information receiverfor receiving the port number differential information, and wherein thereply packet transmitter transmits the reply packet to ports in a rangeindicated by the range information; and the reply packet transmittertransmits the reply packet every port number differential indicated bythe port number differential information.
 2. A communication systemcomprising: a first information processor; a second informationprocessor; a server; a first communication control unit for controllingthe communication of the first information processor; and a secondcommunication control unit for controlling the communication of thesecond information processor, wherein the first information processorincludes: a bubble packet transmitter for transmitting a bubble packetfor leaving transmission record in the first communication control unitto the second communication control unit via the first communicationcontrol unit, and a reply packet receiver for receiving a reply packettransmitted from the second information processor via the secondcommunication control unit to a bubble packet transmitting port, a portof the first communication control unit, which is used in transmissionof the bubble packet, a range detection packet transmitter fortransmitting a range detection packet used for detecting a range ofports including the bubble packet transmitting port to the server; adetection port information receiver for receiving detection portinformation showing a port position of the first communication controlunit through which the range detection packet has passed; a rangedetector for detecting the range of ports including the bubble packettransmitting port in accordance with detection port information receivedby the detection port information receiver; a range transmitter fortransmitting range information detected by the range detector asinformation showing the range of ports including the bubble transmittingport, a port number differential detection packet transmitter fortransmitting a port number differential detection packet for detecting aport number differential in the first communication control unit to theserver via the first communication control unit; a port differentialinformation detector port information receiver for receiving portdifferential information detector port information showing the portposition of the first communication control unit through which the portnumber differential detection packet has passed; a port numberdifferential detector for detecting the port number differential in thefirst communication control unit in accordance with port differentialinformation detector port information received by the port differentialinformation detector port information receiver; and a port numberdifferential information transmitter for transmitting port numberdifferential information detected by the port number differentialdetector as information showing the port number differential of thefirst communication control unit to the second information processor viathe server, the server includes: a detection port detector whichreceives the range detection packet for detecting the port position ofthe first communication control unit through which the range detectionpacket has passed; a detection port information transmitter fortransmitting detection port information showing the port positiondetected by the detection port detector to the first informationprocessor; a port differential information detector port detector whichreceives the port number differential detection packet for detecting theport position of the first communication control unit through which theport number differential detection packet has passed in accordance withthe port number differential detection packet; and a port differentialinformation detector port information transmitter for transmitting portdifferential information detector port information showing the portposition detected by the port differential information detector portdetector to the first information processor, the second informationprocessor includes: a reply packet transmitter for transmitting thereply packet to one or more ports including at least the bubble packettransmitting port; a range receiver for receiving the range information;and a port number differential information receiver for receiving theport number differential information, wherein the reply packettransmitter transmits the reply packet to ports in the range indicatedby the range information, and the reply packet transmitter transmits thereply packet every port number differential indicated by the port numberdifferential information.
 3. A first information processor communicatingwith a second information processor via a first communication controlunit for controlling the communication of the first informationprocessor and a second communication control unit for controlling thecommunication of the second information processor, the first informationprocessor comprising: a bubble packet transmitter for transmitting abubble packet for leaving transmission record in the first communicationcontrol unit to the second communication control unit via the firstcommunication control unit; a range detection packet transmitter fortransmitting a range detection packet used for detecting a range ofports including a bubble packet transmitting port; a reply packetreceiver for receiving a reply packet transmitted from the secondinformation processor via the second communication control unit to thebubble packet transmitting port, a port of the first communicationcontrol unit, which is used in transmission of the bubble packet; and aport number differential detection packet transmitter for transmitting aport number differential detection packet for detecting a port numberdifferential in the first communication control unit to a server via thefirst communication control unit.
 4. A first information processorcommunicating with a second information processor via a firstcommunication control unit for controlling the communication of thefirst information processor and a second communication control unit forcontrolling the communication of the second information processor, thefirst information processor comprising: a bubble packet transmitter fortransmitting a bubble packet for leaving transmission record in thefirst communication control unit to the second communication controlunit via the first communication control unit; a range detection packettransmitter for transmitting a range detection packet used for detectinga range of ports including a bubble packet transmitting port; a replypacket receiver for receiving a reply packet transmitted from the secondinformation processor via the second communication control unit to thebubble packet transmitting port, a port of the first communicationcontrol unit, which is used in transmission of the bubble packet; a portnumber differential detection packet transmitter for transmitting a portnumber differential detection packet for detecting a port numberdifferential in the first communication control unit to a server via thefirst communication control unit; a port differential informationdetector port information receiver for receiving port differentialinformation detector port information showing a port position of thefirst communication control unit through which the port numberdifferential detection packet has passed; a port number differentialdetector for detecting the port number differential in the firstcommunication control unit in accordance with port differentialinformation detector port information received by the port differentialinformation detector port information receiver; and a port numberdifferential information transmitter for transmitting port numberdifferential information detected by the port number differentialdetector as information showing the port number differential of thefirst communication control unit to the second information processor viathe server.
 5. A first information processor communicating with a secondinformation processor via a first communication control unit forcontrolling the communication of the first information processor and asecond communication control unit for controlling the communication ofthe second information processor, wherein a bubble packet for leavingcommunication record in the second communication control unit istransmitted from the second information processor to the firstcommunication control unit via the second communication control unit,the first information processor comprising: a reply packet transmitterfor transmitting a reply packet to one or more ports including at leasta port of the second communication control unit used in transmission ofthe bubble packet from the second information processor; a port numberdifferential information receiver for receiving port number differentialinformation showing a port number differential for transmitting thereply packet, and a range receiver for receiving range informationshowing a range of ports for transmitting the reply packet, wherein thereply packet transmitter transmits the reply packet to ports in therange indicated by the range information, and the reply packettransmitter transmits the reply packet every port number differentialindicated by the port number differential information.
 6. A firstinformation processor communicating with a second information processorvia a first communication control unit for controlling the communicationof the first information processor and a second communication controlunit for controlling the communication of the second informationprocessor, wherein a bubble packet for leaving communication record inthe second communication control unit is transmitted from the secondinformation processor to the first communication control unit via thesecond communication control unit, first information processorcomprising: a reply packet transmitter for transmitting a reply packetto one or more ports including at least a port of the secondcommunication control unit used in transmission of the bubble packetfrom the second information processor; and a port number differentialinformation receiver for receiving port number differential informationshowing a port number differential for transmitting the reply packet,wherein the reply packet transmitter transmits the reply packet everyport number differential indicated by the port number differentialinformation.
 7. A communication method used in an information processorof a communication system, the communication system including aninformation processor, a communication control unit for controlling thecommunication of the information processor, and a server, the methodcomprising the steps of: a bubble packet transmitting step fortransmitting a bubble packet for leaving transmission record in thecommunication control unit via the communication control unit; a rangedetection packet transmitting step for transmitting a range detectionpacket used for detecting a range of ports including a bubble packettransmitting port; a reply packet receiving step for receiving a replypacket transmitted to one or more ports including at least the bubblepacket transmitting port; and a port number differential detectionpacket transmitting step for transmitting a port number differentialdetection packet for detecting a port number differential in thecommunication control unit to the server via the communication controlunit.
 8. A communication method used in an information processor of acommunication system, the communication system including an informationprocessor, a communication control unit for controlling a communicationof the information processor, and a server, the method comprising thesteps of: a bubble packet transmitting step for transmitting a bubblepacket for leaving transmission record in the communication control unitvia the communication control unit; a range detection packettransmitting step for transmitting a range detection packet used fordetecting a range of ports including a bubble packet transmitting port;a reply packet receiving step for receiving a reply packet transmittedto one or more ports including at least the bubble packet transmittingport; and a port number differential detection packet transmitting stepfor transmitting a port number differential detection packet fordetecting a port number differential in the communication control unitto the server via the communication control unit; a detection portinformation receiving step for receiving detection port informationshowing a port position of the communication control unit through whichthe range detection packet has passed; a range detecting step fordetecting the range of ports including the bubble packet transmittingport in accordance with detection port information received by thedetection port information receiving step; and a range transmitting stepfor transmitting range information detected by the range detecting stepas information showing the range of ports including the bubble packettransmitting port.
 9. A communication method used in an informationprocessor of a communication system, the communication system includingan information processor, a communication control unit for controllingthe communication of the information processor, and a server, the methodcomprising the steps of: a bubble packet transmitting step fortransmitting a bubble packet for leaving transmission record in thecommunication control unit via the communication control unit; a rangedetection packet transmitting step for transmitting a range detectionpacket used for detecting a range of ports including a bubble packettransmitting port; a reply packet receiving step for receiving a replypacket transmitted to one or more ports including at least the bubblepacket transmitting port; a port number differential detection packettransmitting step for transmitting a port number differential detectionpacket for detecting a port number differential in the communicationcontrol unit to the server via the communication control unit; a portdifferential information detector port information receiving step forreceiving port differential information detector port informationshowing a port position of the communication control unit through whichthe port number differential detection packet has passed; a port numberdifferential detecting step for detecting the port number differentialin the communication control unit in accordance with port differentialinformation detector port information received by the port differentialinformation detector port information receiving step; and a port numberdifferential transmitting step for transmitting port number differentialinformation detected by the port number differential detecting step asinformation showing the port number differential of the communicationcontrol unit via the server.
 10. A communication method used in a secondinformation processor of a communication system, the communicationsystem including a first information processor, a communication controlunit for controlling the communication of the first informationprocessor, a second information processor, and a second communicationcontrol unit for controlling the communication of the second informationprocessor, wherein a bubble packet for leaving communication record inthe second communication control unit is transmitted from the secondinformation processor to the first communication control unit via thesecond communication control unit, the method comprising the steps of: areply packet transmitting step for transmitting a reply packet to one ormore ports including at least a port of the second communication controlunit used in transmission of the bubble packet from the secondinformation processor; a range receiving step for receiving rangeinformation showing a port range for transmitting the reply packet; anda port number differential receiving step for receiving port numberdifferential information showing a port number differential fortransmitting the reply packet, wherein the reply packet is transmittedto ports in the range indicated by the range information in the replypacket transmitting step, and the reply packet is transmitted every portnumber differential indicated by the port number differentialinformation in the reply packet transmitting step.
 11. A communicationsystem comprising: a first information processor, a second informationprocessor, a first communication control unit for controlling thecommunication of the first information processor, a second communicationcontrol unit for controlling the communication of the second informationprocessor, and a server for establishing communication between the firstinformation processor and the second information processor, wherein thefirst information processor includes: a bubble packet transmitter fortransmitting a bubble packet, for leaving transmission record in thefirst communication control unit, to the second communication controlunit via the first communication control unit; a range detection packettransmitter for transmitting a range detection packet to the serverafter the transmission of the bubble packet, the range detection packetbeing used for detecting a range of ports including a bubble packettransmitting port, the bubble packet transmitting port being a port ofthe first communication control unit and used for transmission of thebubble packet; a reply packet receiver for receiving a reply packettransmitted from the second information processor via the secondcommunication control unit to the bubble packet transmitting port, andwherein a port position of the first communication control unit used intransmission of the range detection packet is different from a positionof the bubble packet transmitting port, and the server includes: a rangedetector which receives the range detection packet for detecting therange having an upper limit or a lower limit, of a plurality of portsincluding the bubble packet transmitting port in accordance with therange detection packet; a range transmitter for transmitting rangeinformation, detected by the range detector as information showing therange, to the second information processor, and the second informationprocessor includes: a range receiver for receiving the rangeinformation; a reply packet transmitter for transmitting the replypacket to at least one or more ports including the bubble packettransmitting port, and wherein the reply packet transmitter transmitsthe reply packet to ports in the range indicated by the rangeinformation.
 12. The communication system of claim 11, wherein the rangedetection packet transmitter of the first information processor furthertransmits the range detection packet before transmission of the bubblepacket, the server receives the range detection packet transmittedbefore and after transmission of the bubble packet, the range detectordetects the range of ports including the bubble packet transmitting portin accordance with the range detection packet, and the range transmittertransmits range information detected by the range detector asinformation showing the range of ports including the bubble packettransmitting port to the second information processor.
 13. Acommunication method used in a second information processor of acommunication system, the communication system including a firstinformation processor, a second information processor, a firstcommunication control unit for controlling the communication of thefirst information processor, a second communication control unit forcontrolling the communication of the second information processor, and aserver for establishing communication between the first informationprocessor and the second information processor, the method comprisingthe steps of: a bubble packet transmitting step of transmitting a bubblepacket to the second communication control unit via a bubble packettransmitting port of the first communication control unit, the bubblepacket being used for leaving transmission record in the firstcommunication control unit; a range detection packet transmitting stepof transmitting a range detection packet to the server via a rangedetection transmitting port, having a position different than theposition of the bubble packet transmitting port, after the transmissionof the bubble packet, the range detection packet for detecting a rangeof ports including the bubble packet transmitting port; a reply packetreceiving step of receiving a reply packet transmitted from the secondinformation processor via the second communication control unit to thebubble packet transmitting port; a range detector receiving step ofreceiving, at the server, the range detection packet for detecting therange, having an upper limit or a lower limit, of a plurality of portsincluding the bubble packet transmitting port in accordance with therange detection packet; a range transmitting step for transmitting rangeinformation, detected by the range detector receiving step asinformation showing the range, from the server to the second informationprocessor; a range receiving step of receiving the range information atthe second information processor; and a reply packet transmitting stepof transmitting the reply packet from the second information processorto at least one or more ports in the range indicated by the rangeinformation, including the bubble packet transmitting port.
 14. Thecommunication method of claim 13, further comprising the steps of:transmitting, by the range detection packet transmitting step, the rangedetection packet before transmission of the bubble packet, receiving, atthe server, the range detection packet transmitted before and aftertransmission of the bubble packet, detecting, by the range detectorreceiving step, the range of ports including the bubble packettransmitting port in accordance with the range detection packet, andtransmitting, by the range transmitting step, range information detectedby the range detector receiving step as information showing the range ofports including the bubble packet transmitting port to the secondinformation processor.